refactor: merge mozilla-central http3 server into neqo-bin

There are two server implementations based on neqo:

1. https://github.com/mozilla/neqo/tree/main/neqo-bin/src/server
  - http3 and http09 implementation
  - used for manual testing and QUIC Interop

2. https://searchfox.org/mozilla-central/source/netwerk/test/http3server/src/main.rs
  - used to test Firefox

I assume one was once an exact copy of the other. Both implement their own I/O,
event loop, ... Since then, the two implementations diverged significantly.
Especially (1) saw a lot of improvements in recent months:

- mozilla#1564
- mozilla#1569
- mozilla#1578
- mozilla#1581
- mozilla#1604
- mozilla#1612
- mozilla#1676
- mozilla#1692
- mozilla#1707
- mozilla#1708
- mozilla#1727
- mozilla#1753
- mozilla#1756
- mozilla#1766
- mozilla#1772
- mozilla#1786
- mozilla#1787
- mozilla#1788
- mozilla#1794
- mozilla#1806
- mozilla#1808
- mozilla#1848
- mozilla#1866

At this point, bugs in (2) are hard to fix, see e.g.
mozilla#1801.

This commit merges (2) into (1), thus removing all duplicate logic and
having (2) benefit from all the recent improvements to (1).

neqo-bin/Cargo.toml

@@ -39,6 +39,10 @@ quinn-udp = { git = "https://github.com/quinn-rs/quinn/", rev = "a947962131aba8a
 regex = { version = "1.9", default-features = false, features = ["unicode-perl"] }
 tokio = { version = "1", default-features = false, features = ["net", "time", "macros", "rt", "rt-multi-thread"] }
 url = { version = "2.5", default-features = false }
+# TODO: Consider feature flagging. Definitely reduce feature set.
+hyper = { version = "0.14", features = ["full"] }
+# TODO: sort?
+cfg-if = "1.0"
 
 [dev-dependencies]
 criterion = { version = "0.5", default-features = false, features = ["html_reports", "async_tokio"] }