mbedtls: add more informative logging

mbedtls: add more informative logging

After TLS handshare, indicate which TLS version was negotiated in
addition to the cipher in the handshake completed log message.

Also use the verify callback for certificate logging and collection.
This allows things to work even when MBEDTLS_SSL_KEEP_PEER_CERTIFICATE
is disabled in the mbedtls library.

And lastly, catch certificate validation errors later so we can give the
user more informative error messages that indicate what the failure was
from certificate validation.

Tested on both current LTS versions (2.28 and 3.6).

Closes #14444