Code which targets OpenSSL won't use EVP_parse_public_key. X509_PUBKEY
is fairly deeply tied to the old ASN.1 stack, but there's no reason for
i2d_PUBKEY and friends to be. Move them to crypto/evp and reimplement as
wrappers over our functions.
Bug: chromium:1102458
Change-Id: Ic11766acdac797602e4abe1253b0efe33faef298
Reviewed-on: https://boringssl-review.googlesource.com/c/boringssl/+/42005
Commit-Queue: David Benjamin <davidben@google.com>
Reviewed-by: Adam Langley <agl@google.com>