Add a generic AEAD test that exercises the vectors for AES GCM, ChaCha20Poly-1305, and XChaCha20-Poly1305. Removes the existing chacha20_poly1305_test.go test. Change-Id: Icfaba30f8db2a1e32a9459c98cd3af5d63052027 Reviewed-on: https://go-review.googlesource.com/c/crypto/+/234688 Run-TryBot: Katie Hockman <katie@golang.org> TryBot-Result: Gobot Gobot <gobot@golang.org> Reviewed-by: Katie Hockman <katie@golang.org>