gh-116333: Relax error string text expectations in SSL-related tests

[WillChilds-Klein]

Description

As suggested here, this change relaxes the OpenSSL error string text expectations in a number of tests. This was specifically done in support of more easily building CPython AWS-LC, but because AWS-LC is a fork of BoringSSL, it should increase compatibility with that library as well.

In addition to the error string relaxations, we also add some guards around the tls-unique channel binding being used with TLSv1.3, as that feature (described in RFC 6929) is not defined for TLSv1.3.

Call-outs

I've omitted a NEWS entry as this PR does not change anything for end users, and does not fully provide out-of-the box support for AWS-LC on its own.

Testing

• CPython CI
• local testing with AWS-LC (additional patch required)
  • some tests still fail in local testing, but this is expected due to AWS-LC's present lack of support for TLSv1.3 post-handshake authentication
• local testing with system ssl

system info

$ openssl version && uname -r && cat /etc/*release
OpenSSL 3.0.2 15 Mar 2022 (Library: OpenSSL 3.0.2 15 Mar 2022)
6.2.0-1014-aws
DISTRIB_ID=Ubuntu
DISTRIB_RELEASE=22.04
DISTRIB_CODENAME=jammy
DISTRIB_DESCRIPTION="Ubuntu 22.04.2 LTS"
PRETTY_NAME="Ubuntu 22.04.2 LTS"
NAME="Ubuntu"
VERSION_ID="22.04"
VERSION="22.04.2 LTS (Jammy Jellyfish)"
VERSION_CODENAME=jammy
ID=ubuntu
ID_LIKE=debian
HOME_URL="https://www.ubuntu.com/"
SUPPORT_URL="https://help.ubuntu.com/"
BUG_REPORT_URL="https://bugs.launchpad.net/ubuntu/"
PRIVACY_POLICY_URL="https://www.ubuntu.com/legal/terms-and-policies/privacy-policy"
UBUNTU_CODENAME=jammy

• Issue: Relax error string text expectations in SSL-related tests #116333