Share common functions/structs between ngtcp2 HTTP/3 and the proxy
version.
Fix bugs in proxy implementation when it comes to stream and pollset
handling and transfer lifetimes.
Curl_multi_xfer_sockbuf_borrow: work without multi
When a connection gets shutdown by a share, the easy handle used is
share->admin and it does not have a multi handle. In that case let
Curl_multi_xfer_sockbuf_borrow() allocate a buffer to be freed on
release.
This happens when a TLS filter sends its last notify through a HTTP/3
proxy tunnel.
Closes#21871
cert_type, key, key_type, key_passwd and key_blob lived in
ssl_config_data but not in ssl_primary_config, so they were invisible to
match_ssl_primary_config() and to the TLS session cache peer key.
Two easy handles sharing a connection pool could reuse each other's
authenticated connections when they differed only on SSLKEY, SSLKEYTYPE,
KEYPASSWD, SSLCERTTYPE or SSLKEYBLOB. The second handle would silently
inherit the first handle's authenticated identity.
Promote all five fields into ssl_primary_config so the conn-reuse
predicate and session cache key cover the complete client credential
set. Also replace the fixed ":CCERT" session cache marker with the
actual clientcert path so sessions are not shared across different
client certificates.
Verified by test 3303 and 3304
Reported-By: Joshua Rogers (AISLE Research)
Closes#21667
