crypto: use encoding append functions
Replace custom append functions in the hash functions with the implementation of the encoding/binary package that do the same thing.
The binary bigendian functions are already used in other parts of the code in the crypto package.
Change-Id: I76d2dbe143fc72a3b4ac06be312caf72bd71378a
GitHub-Last-Rev:
1c6c68279efbe2c5835d82db900f607c7bf36836
GitHub-Pull-Request: golang/go#55085
Reviewed-on: https://go-review.googlesource.com/c/go/+/431035
Run-TryBot: Ian Lance Taylor <iant@google.com>
Reviewed-by: Keith Randall <khr@google.com>
Auto-Submit: Ian Lance Taylor <iant@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@google.com>