Standards compliance & bug fixes

We now score 158/159 in the external Http11Probe standards compliance test. The last remaining check is skipped due to being out-of-scope:

What's Changed

Accept any transfer-encoding ending in chunked by @cpruijsen in #1943
Add missing cstdint include for uint64_t by @glingy in #1860
Support valueless queries by @Dev-next-gen in #1944
Copilot/add 502 bad gateway error page by @uNetworkingAB in #1947
Skip trailer fields after the last chunk, and answer 400 to a bare LF in them by @nigrosimone in #1950
Answer 400 to a request target that is not visible ASCII by @nigrosimone in #1951
Reject a Host header with a path, a query or a fragment by @nigrosimone in #1949
Add missing return in TemplatedApp move assignment operator by @Dev-next-gen in #1946
Accept the asterisk form for OPTIONS by @nigrosimone in #1952
Preserve per-connection WebSocket compressor selection by @akorzynski in #1955

Full Changelog: v20.80.0...v20.81.0