TLS tests: detect reactor and protocol capabilities directly

[dkropachev]

Harden TLS-resumption tests by checking actual capabilities instead of configuration assumptions:

• Skip integration coverage from connection_class.supports_tls_session_resumption, not only EVENT_LOOP_MANAGER.
• Guard TLS 1.3 tests with ssl.HAS_TLSv1_3.

Follow-up to #426.