regexp: limit size of parsed regexps

regexp: limit size of parsed regexps

Set a 128 MB limit on the amount of space used by []syntax.Inst
in the compiled form corresponding to a given regexp.

Also set a 128 MB limit on the rune storage in the *syntax.Regexp
tree itself.

Thanks to Adam Korczynski (ADA Logics) and OSS-Fuzz for reporting this issue.

Fixes CVE-2022-41715.
Fixes #55949.

Change-Id: Ia656baed81564436368cf950e1c5409752f28e1b
Reviewed-on: https://go-review.googlesource.com/c/go/+/439356
Auto-Submit: Roland Shoemaker <roland@golang.org>
TryBot-Result: Gopher Robot <gobot@golang.org>
Run-TryBot: Roland Shoemaker <roland@golang.org>
Reviewed-by: Damien Neil <dneil@google.com>