crypto/sha3: new package

crypto/sha3: new package

Implement the SHA-3 hash algorithms and the SHAKE extendable output
functions defined in FIPS 202.

This is a wrapper for crypto/internal/fips/sha3 which in turn was ported
from x/crypto/sha3 in CL 616717 as part of #65269.

Fixes #69982

Change-Id: I64ce7f362c1a773f7f5b05f7e0acb4110e52a329
Reviewed-on: https://go-review.googlesource.com/c/go/+/629176
Reviewed-by: Russ Cox <rsc@golang.org>
Auto-Submit: Filippo Valsorda <filippo@golang.org>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>