crypto/aes,crypto/cipher: test all available implementations

crypto/aes,crypto/cipher: test all available implementations

TestEmptyPlaintext and TestCryptBlocks were folded into cryptotest.

Change-Id: I6131ab8582eb0e6d3a1b24bab1147a145d9766ac
Reviewed-on: https://go-review.googlesource.com/c/go/+/624738
Reviewed-by: Roland Shoemaker <roland@golang.org>
Reviewed-by: Daniel McCarney <daniel@binaryparadox.net>
Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>
Auto-Submit: Filippo Valsorda <filippo@golang.org>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>