Certificate Compression for QUIC

[larseggert]

See https://bugzilla.mozilla.org/show_bug.cgi?id=1927797

This is currently not implemented. Discussed with @martinthomson and we should do this inside neqo_glue by hooking in the same functionality that is used for TLS/TCP.

That means neqo alone won't support it, which is a bit disappointing, but I don't see an easy way to pull in all that code into this repo, and implementing a separate-and-different Rust codepath just for neqo alone seems not useful.