fix(compress): respect Accept-Encoding when encoding option is set (#4951)

* fix(compress): skip compression when client does not accept the configured encoding

When the encoding option is set, the middleware previously compressed responses
unconditionally, regardless of the Accept-Encoding header. This could send a
response in an encoding the client cannot decode (for example, returning gzip
when the client only advertised deflate, or when Accept-Encoding is absent).

Honor the client's Accept-Encoding header even when an encoding is explicitly
configured, falling back to no compression when the configured encoding is
not accepted.

* fix(compress): use parseAccept to honor q-values, wildcard, and case

Address review from @yusukebe. The previous version used String.includes
on the raw Accept-Encoding header, which treated x-gzip as gzip, ignored
q=0 explicit refusals, and did not understand the wildcard. Switch to
parseAccept (already used by accepts middleware) and pick the candidate
encoding with the highest non-zero q value, falling back to the wildcard
q if the candidate has no explicit entry.

Add seven regression tests covering q=0 on the configured encoding, q=0
fallback to another candidate, wildcard \*, case-insensitive tokens,
x-gzip non-matching, highest-q wins, and gzip-over-deflate tie-break.

* fix(compress): short-circuit selectEncoding when q is 1

Per @usualoma: q values are almost always 1 in practice, so short-circuit
and return immediately for the common path instead of continuing to scan
the remaining candidates.


Co-authored-by: Yusuke Wada <yusuke@kamawada.com>
Co-authored-by: Taku Amano <taku@taaas.jp>