Also, add Version to CertificateRequestInfo, as the semantics of
SignatureSchemes change based on version: the ECDSA SignatureSchemes are
only constrained to a specific curve in TLS 1.3.

Fixes #32426

Change-Id: I7a551bea864799e98118349ac2476162893d1ffd
Reviewed-on: https://go-review.googlesource.com/c/go/+/205058
Run-TryBot: Filippo Valsorda <filippo@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Adam Langley <agl@golang.org>