Described in detail in internal doc TLS-SESSIONS.md
Main points:
- use a new `ssl_peer_key` for cache lookups by connection filters
- recognize differences between TLSv1.3 and other tickets
* TLSv1.3 tickets are single-use, cache can hold several of them for a peer
* TLSv1.2 are reused, keep only a single one per peer
- differentiate between ticket BLOB to store (that could be persisted) and object instances
- use put/take/return pattern for cache access
- remember TLS version, ALPN protocol, time received and lifetime of ticket
- auto-expire tickets after their lifetime
Closes#15774
fa0ccd9f1f