test/bench: delete

test/bench: delete

Russ added test/bench/go1 in CL 5484071 to have a stable suite of
programs to use as benchmarks. For the compiler and runtime we had
back then, those were reasonable benchmarks, but the compiler and
runtime are now far more sophisticated and these benchmarks no longer
have good coverage. We also now have better benchmark suites
maintained outside the repo (e.g., golang.org/x/benchmarks). Keeping
test/bench/go1 at this point is actively misleading.

Indirectly related to #37486, as this also removes the last package
dist test runs outside of src/.

Change-Id: I2867ef303fe48a02acce58ace4ee682add8acdbf
Reviewed-on: https://go-review.googlesource.com/c/go/+/494193
Run-TryBot: Austin Clements <austin@google.com>
Reviewed-by: Cherry Mui <cherryyz@google.com>
Reviewed-by: Russ Cox <rsc@golang.org>
TryBot-Result: Gopher Robot <gobot@golang.org>