quic: convert incoming :status header to number

[hallss93]

Fixes: #63557

Summary

When receiving HTTP/3 headers via QUIC, headers[':status'] was exposed as a
string. HTTP/2 converts the incoming :status pseudo-header to a number in
toHeaderObject() (lib/internal/http2/util.js). This mismatch makes it
awkward to port HTTP/2 code to HTTP/3.

Align HTTP/3 with HTTP/2 by converting :status to a number in
parseHeaderPairs() when building the header object from C++ name/value
pairs. This applies to initial response headers, informational (1xx)
headers (oninfo), and stream.headers.

Outgoing headers are unchanged: callers may still pass ':status': '200' or
':status': 200 when calling sendHeaders() / sendInformationalHeaders().

Test plan

• Update existing QUIC H3 tests to expect numeric :status on receive

• Add test/parallel/test-quic-h3-status-code-type.mjs covering 200, 204, and 404

• Run (with QUIC enabled):

  node --experimental-quic --experimental-stream-iter --no-warnings \
    test/parallel/test-quic-h3-status-code-type.mjs \
    test/parallel/test-quic-h3-header-validation.mjs \
    test/parallel/test-quic-h3-informational-headers.mjs \
    test/parallel/test-quic-h3-request-response.mjs

[nodejs-github-bot]

Review requested:

• @nodejs/quic