Keeping it to X25519/Ed25519 for now, but arguably we could pick "raw"
options for most of our keys. The problem is just when there's a couple
different options. (ECPrivateKey or just the serialized scalar for EC
keys, compressed vs uncompressed points.)
Bug: 42290364
Change-Id: I1e1a0a3fa971f27a962946301091ebe11bac2725
Reviewed-on: https://boringssl-review.googlesource.com/c/boringssl/+/81667
Commit-Queue: David Benjamin <davidben@google.com>
Reviewed-by: Adam Langley <agl@google.com>