If a client or server explicitly offers point formats, and the point
formats don't include the uncompressed format, then error. This matches
BoringSSL and Rustls behaviour and allows enabling the
PointFormat-Client-MissingUncompressed bogo test.

Updates #72006

Change-Id: I27a2cd231e4b8762b0d9e2dbd3d8ddd5b87fd5c5
Reviewed-on: https://go-review.googlesource.com/c/go/+/669157


Reviewed-by: Roland Shoemaker <roland@golang.org>
Reviewed-by: Cherry Mui <cherryyz@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>