compress: reduce copies of new text for compression testing

compress: reduce copies of new text for compression testing

The previous book was 387 KiB decompressed and 119 KiB compressed, the
new book is 567 KiB decompressed and 132 KiB compressed. Overall, this
change will reduce the release binary size by 196 KiB. The new book will
allow for slightly more extensive compression testing with a larger
text.

Command to run the benchmark tests used with benchstat:
`../bin/go test -run='^$' -count=4 -bench=. compress/bzip2 compress/flate`

When running the benchmarks locally, changed "Newton" to "Twain" and
filtered the tests with the -bench flag to include only those which were
relevant to these changes.

benchstat results below:

name                            old time/op    new time/op     delta
DecodeTwain-8                     19.6ms ± 2%     24.1ms ± 1%  +23.04%  (p=0.029 n=4+4)
Decode/Twain/Huffman/1e4-8         140µs ± 3%      139µs ± 5%     ~     (p=0.886 n=4+4)
Decode/Twain/Huffman/1e5-8        1.27ms ± 3%     1.26ms ± 1%     ~     (p=1.000 n=4+4)
Decode/Twain/Huffman/1e6-8        12.4ms ± 0%     13.2ms ± 1%   +6.42%  (p=0.029 n=4+4)
Decode/Twain/Speed/1e4-8           133µs ± 1%      123µs ± 1%   -7.35%  (p=0.029 n=4+4)
Decode/Twain/Speed/1e5-8          1.20ms ± 0%     1.02ms ± 3%  -15.32%  (p=0.029 n=4+4)
Decode/Twain/Speed/1e6-8          12.0ms ± 2%     10.1ms ± 3%  -15.89%  (p=0.029 n=4+4)
Decode/Twain/Default/1e4-8         131µs ± 6%      108µs ± 5%  -17.84%  (p=0.029 n=4+4)
Decode/Twain/Default/1e5-8        1.06ms ± 2%     0.80ms ± 1%  -24.97%  (p=0.029 n=4+4)
Decode/Twain/Default/1e6-8        10.0ms ± 3%      8.0ms ± 3%  -20.06%  (p=0.029 n=4+4)
Decode/Twain/Compression/1e4-8     128µs ± 4%      115µs ± 4%   -9.70%  (p=0.029 n=4+4)
Decode/Twain/Compression/1e5-8    1.04ms ± 2%     0.83ms ± 4%  -20.37%  (p=0.029 n=4+4)
Decode/Twain/Compression/1e6-8    10.4ms ± 4%      8.1ms ± 5%  -22.25%  (p=0.029 n=4+4)
Encode/Twain/Huffman/1e4-8        55.7µs ± 2%     55.6µs ± 1%     ~     (p=1.000 n=4+4)
Encode/Twain/Huffman/1e5-8         441µs ± 0%      435µs ± 2%     ~     (p=0.343 n=4+4)
Encode/Twain/Huffman/1e6-8        4.31ms ± 4%     4.30ms ± 4%     ~     (p=0.886 n=4+4)
Encode/Twain/Speed/1e4-8           193µs ± 1%      166µs ± 2%  -14.09%  (p=0.029 n=4+4)
Encode/Twain/Speed/1e5-8          1.54ms ± 1%     1.22ms ± 1%  -20.53%  (p=0.029 n=4+4)
Encode/Twain/Speed/1e6-8          15.3ms ± 1%     12.2ms ± 3%  -20.62%  (p=0.029 n=4+4)
Encode/Twain/Default/1e4-8         393µs ± 1%      390µs ± 1%     ~     (p=0.114 n=4+4)
Encode/Twain/Default/1e5-8        6.12ms ± 4%     6.02ms ± 5%     ~     (p=0.486 n=4+4)
Encode/Twain/Default/1e6-8        69.4ms ± 5%     59.0ms ± 4%  -15.07%  (p=0.029 n=4+4)
Encode/Twain/Compression/1e4-8     423µs ± 2%      379µs ± 2%  -10.34%  (p=0.029 n=4+4)
Encode/Twain/Compression/1e5-8    7.00ms ± 1%     7.88ms ± 3%  +12.49%  (p=0.029 n=4+4)
Encode/Twain/Compression/1e6-8    76.6ms ± 5%     80.9ms ± 3%     ~     (p=0.114 n=4+4)

name                            old speed      new speed       delta
DecodeTwain-8                   19.8MB/s ± 2%   23.6MB/s ± 1%  +18.84%  (p=0.029 n=4+4)
Decode/Twain/Huffman/1e4-8      71.7MB/s ± 3%   72.1MB/s ± 6%     ~     (p=0.943 n=4+4)
Decode/Twain/Huffman/1e5-8      78.8MB/s ± 3%   79.5MB/s ± 1%     ~     (p=1.000 n=4+4)
Decode/Twain/Huffman/1e6-8      80.5MB/s ± 0%   75.6MB/s ± 1%   -6.03%  (p=0.029 n=4+4)
Decode/Twain/Speed/1e4-8        75.2MB/s ± 1%   81.2MB/s ± 1%   +7.93%  (p=0.029 n=4+4)
Decode/Twain/Speed/1e5-8        83.4MB/s ± 0%   98.6MB/s ± 3%  +18.16%  (p=0.029 n=4+4)
Decode/Twain/Speed/1e6-8        83.6MB/s ± 2%   99.5MB/s ± 3%  +18.91%  (p=0.029 n=4+4)
Decode/Twain/Default/1e4-8      76.3MB/s ± 6%   92.8MB/s ± 4%  +21.62%  (p=0.029 n=4+4)
Decode/Twain/Default/1e5-8      94.4MB/s ± 3%  125.7MB/s ± 1%  +33.24%  (p=0.029 n=4+4)
Decode/Twain/Default/1e6-8       100MB/s ± 3%    125MB/s ± 3%  +25.12%  (p=0.029 n=4+4)
Decode/Twain/Compression/1e4-8  78.4MB/s ± 4%   86.8MB/s ± 4%  +10.73%  (p=0.029 n=4+4)
Decode/Twain/Compression/1e5-8  95.7MB/s ± 2%  120.3MB/s ± 4%  +25.65%  (p=0.029 n=4+4)
Decode/Twain/Compression/1e6-8  96.4MB/s ± 4%  124.0MB/s ± 5%  +28.64%  (p=0.029 n=4+4)
Encode/Twain/Huffman/1e4-8       179MB/s ± 2%    180MB/s ± 1%     ~     (p=1.000 n=4+4)
Encode/Twain/Huffman/1e5-8       227MB/s ± 0%    230MB/s ± 2%     ~     (p=0.343 n=4+4)
Encode/Twain/Huffman/1e6-8       232MB/s ± 4%    233MB/s ± 4%     ~     (p=0.886 n=4+4)
Encode/Twain/Speed/1e4-8        51.8MB/s ± 1%   60.4MB/s ± 2%  +16.43%  (p=0.029 n=4+4)
Encode/Twain/Speed/1e5-8        65.1MB/s ± 1%   81.9MB/s ± 1%  +25.83%  (p=0.029 n=4+4)
Encode/Twain/Speed/1e6-8        65.2MB/s ± 1%   82.2MB/s ± 3%  +26.00%  (p=0.029 n=4+4)
Encode/Twain/Default/1e4-8      25.4MB/s ± 1%   25.6MB/s ± 1%     ~     (p=0.114 n=4+4)
Encode/Twain/Default/1e5-8      16.4MB/s ± 4%   16.6MB/s ± 5%     ~     (p=0.486 n=4+4)
Encode/Twain/Default/1e6-8      14.4MB/s ± 6%   17.0MB/s ± 4%  +17.67%  (p=0.029 n=4+4)
Encode/Twain/Compression/1e4-8  23.6MB/s ± 2%   26.4MB/s ± 2%  +11.54%  (p=0.029 n=4+4)
Encode/Twain/Compression/1e5-8  14.3MB/s ± 1%   12.7MB/s ± 3%  -11.08%  (p=0.029 n=4+4)
Encode/Twain/Compression/1e6-8  13.1MB/s ± 4%   12.4MB/s ± 3%     ~     (p=0.114 n=4+4)

name                            old alloc/op   new alloc/op    delta
DecodeTwain-8                     3.63MB ± 0%     3.63MB ± 0%   +0.15%  (p=0.029 n=4+4)
Decode/Twain/Huffman/1e4-8        42.0kB ± 0%     41.3kB ± 0%   -1.62%  (p=0.029 n=4+4)
Decode/Twain/Huffman/1e5-8        43.5kB ± 0%     45.1kB ± 0%   +3.74%  (p=0.029 n=4+4)
Decode/Twain/Huffman/1e6-8        71.7kB ± 0%     80.0kB ± 0%  +11.55%  (p=0.029 n=4+4)
Decode/Twain/Speed/1e4-8          41.2kB ± 0%     41.3kB ± 0%     ~     (p=0.286 n=4+4)
Decode/Twain/Speed/1e5-8          45.1kB ± 0%     43.9kB ± 0%   -2.80%  (p=0.029 n=4+4)
Decode/Twain/Speed/1e6-8          72.8kB ± 0%     81.3kB ± 0%  +11.72%  (p=0.029 n=4+4)
Decode/Twain/Default/1e4-8        41.2kB ± 0%     41.2kB ± 0%   -0.22%  (p=0.029 n=4+4)
Decode/Twain/Default/1e5-8        44.4kB ± 0%     43.0kB ± 0%   -3.02%  (p=0.029 n=4+4)
Decode/Twain/Default/1e6-8        71.0kB ± 0%     61.8kB ± 0%  -13.00%  (p=0.029 n=4+4)
Decode/Twain/Compression/1e4-8    41.3kB ± 0%     41.2kB ± 0%   -0.29%  (p=0.029 n=4+4)
Decode/Twain/Compression/1e5-8    43.3kB ± 0%     43.0kB ± 0%   -0.72%  (p=0.029 n=4+4)
Decode/Twain/Compression/1e6-8    69.1kB ± 0%     63.7kB ± 0%   -7.90%  (p=0.029 n=4+4)

name                            old allocs/op  new allocs/op   delta
DecodeTwain-8                       51.0 ± 0%       51.2 ± 1%     ~     (p=1.000 n=4+4)
Decode/Twain/Huffman/1e4-8          15.0 ± 0%       14.0 ± 0%   -6.67%  (p=0.029 n=4+4)
Decode/Twain/Huffman/1e5-8          20.0 ± 0%       23.0 ± 0%  +15.00%  (p=0.029 n=4+4)
Decode/Twain/Huffman/1e6-8           134 ± 0%        161 ± 0%  +20.15%  (p=0.029 n=4+4)
Decode/Twain/Speed/1e4-8            17.0 ± 0%       18.0 ± 0%   +5.88%  (p=0.029 n=4+4)
Decode/Twain/Speed/1e5-8            30.0 ± 0%       31.0 ± 0%   +3.33%  (p=0.029 n=4+4)
Decode/Twain/Speed/1e6-8             193 ± 0%        228 ± 0%  +18.13%  (p=0.029 n=4+4)
Decode/Twain/Default/1e4-8          17.0 ± 0%       15.0 ± 0%  -11.76%  (p=0.029 n=4+4)
Decode/Twain/Default/1e5-8          28.0 ± 0%       32.0 ± 0%  +14.29%  (p=0.029 n=4+4)
Decode/Twain/Default/1e6-8           199 ± 0%        158 ± 0%  -20.60%  (p=0.029 n=4+4)
Decode/Twain/Compression/1e4-8      17.0 ± 0%       15.0 ± 0%  -11.76%  (p=0.029 n=4+4)
Decode/Twain/Compression/1e5-8      28.0 ± 0%       32.0 ± 0%  +14.29%  (p=0.029 n=4+4)
Decode/Twain/Compression/1e6-8       196 ± 0%        150 ± 0%  -23.47%  (p=0.029 n=4+4)

Updates #27151

Change-Id: I6c439694ed16a33bb4c63fbfb8570c7de46b4f2d
Reviewed-on: https://go-review.googlesource.com/135495
Reviewed-by: Dmitri Shuralyov <dmitshur@golang.org>
Reviewed-by: Joe Tsai <thebrokentoaster@gmail.com>