Raw Public Keys: Store peer cert type and RPK in SSL_SESSION

This adds the peer's negotiated cert type and peer RPK (if any) to
SSL_SESSION. This is needed for RPKs to be supported in resumption.
The peer RPK field is not yet filled in, but will be after the next CL
implements parsing received RPKs.

For previously serialized session tickets, we assume the peer cert type
was the default (X.509) for backwards compatibility, and we only include
the peer cert type in the serialized session if it was not the default.

Split handshakes are not supported with RPKs.

The previous fields for server/client_cert_type in SSL_HANDSHAKE are
reframed as client_auth_cert_type (storing client_cert_type for a
client) and peer_cert_type (storing the peer's cert type for both
servers and clients). For a server, the server_cert_type doesn't need to
be stored because it's determined by the selected credential.

This removes the previously added OpenSSL-compatible APIs for getting
the negotiated client/server cert type, because now we can't always know
the cert type that we presented to the peer (e.g. in the resumption
case). The negotiated peer cert type should always be determined, so we
provide a new getter for that.

Update-Note: This removes SSL_get_negotiated_client_cert_type() and
SSL_get_negotiated_server_cert_type(), in favor of a new function
SSL_get_peer_cert_type().

Bug: 467663225
Change-Id: If20e597eb858649a491a7dc41f0c2e0c6a6a6964
Reviewed-on: https://boringssl-review.googlesource.com/c/boringssl/+/89831
Reviewed-by: David Benjamin <davidben@google.com>
Commit-Queue: Lily Chen <chlily@google.com>