Add more TLS-specifics

[rmarx]

Currently, we have few options for logging a lot of TLS related data (e.g., cipher suites, supported groups, (E)SNI, ...).

Need to figure out a generic form for TLS (extensions) data so it can be logged using qlog as well.

Note: this is getting in the "new TCP+TLS+HTTP/2 schema" territory

[marten-seemann]

Note that #27 suggests to add some resumption and 0-RTT events, which arguably are TLS-specific. They do however (at least 0-RTT does) change how the QUIC stack behaves, in pretty fundamental ways (namely sending and processing 0-RTT data, restoring transport parameters, etc.), which is a good justification for including these (but not other) events.