tls: introduce client 'session' event
OpenSSL has supported async notification of sessions and tickets since 1.1.0 using SSL_CTX_sess_set_new_cb(), for all versions of TLS. Using the async API is optional for TLS1.2 and below, but for TLS1.3 it will be mandatory. Future-proof applications should start to use async notification immediately. In the future, for TLS1.3, applications that don't use the async API will silently, but gracefully, fail to resume sessions and instead do a full handshake.
See: https://wiki.openssl.org/index.php/TLS1.3#Sessions
Checklist
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make -j4 test
(UNIX), orvcbuild test
(Windows) passes -
tests and/or benchmarks are included -
documentation is changed or added -
commit message follows commit guidelines