http2: refactor outgoing write mechanism

The first commits in this are from #17406. It’s blocked on that merge-conflict-wise but generally ready for review.

• http2: remove redundant write indirection

  nghttp2_stream_write_t was not a necessary redirection layer and came with the cost of one additional allocation per stream write.

  Also, having both nghttp2_stream_write and nghttp2_stream_write_t as identifiers did not help with readability.

    $ ./node benchmark/compare.js --new ./node --old ./node-before --runs 100 --filter write --set streams=20 --set length=1024 --set size=16 http2 | Rscript benchmark/compare.R
    [00:26:09|% 100| 1/1 files | 200/200 runs | 1/1 configs]: Done
                                                                         improvement confidence     p.value
     http2/write.js benchmarker="h2load" size=16 length=1024 streams=20      0.58 %         ** 0.005535241

• http2: refactor outgoing write mechanism

  • Only finish outgoing WriteWraps once data has actually been passed to the underlying socket.

    • This makes HTTP2 streams respect backpressure

  • Use DoTryWrite as a shortcut for sending out as much of the data synchronously without blocking as possible

  • Use NGHTTP2_DATA_FLAG_NO_COPY to avoid copying DATA frame contents into nghttp2’s buffers before sending them out.

    $ ./node benchmark/compare.js --new ./node --old ./node-before --runs 10 --filter write --set streams=20 --set length=1024 --set size=16 http2 | Rscript benchmark/compare.R
    [00:02:30|% 100| 1/1 files | 20/20 runs | 1/1 configs]: Done
                                                                         improvement confidence      p.value
     http2/write.js benchmarker="h2load" size=16 length=1024 streams=20      6.88 %        *** 2.261566e-08

Checklist

• make -j4 test (UNIX), or vcbuild test (Windows) passes
• commit message follows commit guidelines

Affected core subsystem(s)

http2 @nodejs/http2

CI: https://ci.nodejs.org/job/node-test-commit/14902/