Add TLS 1.3-compatible tests for sessions

[chrisnovakovic]

The following tests in the test suite are specific to TLS 1.2 and below due to changes to the session protocol in TLS 1.3:

• t/local/64_ticket_sharing.t
• t/local/65_ticket_sharing_2.t

For completeness, it'd be good to have equivalent tests for TLS 1.3 when the version of libssl in use supports TLS 1.3.