Resolve some of the TODO(QUIC) items

Resolve some of the TODO(QUIC) items

For some of the items we add FUTURE/SERVER/TESTING/MULTIPATH
designation to indicate these do not need to be resolved
in QUIC MVP release.

Reviewed-by: Paul Dale <pauli@openssl.org>
Reviewed-by: Hugo Landau <hlandau@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/21539)