stream: improve writable.write() performance

[mscdex]

Benchmark results:

                                                                                   confidence improvement accuracy (*)   (**)  (***)
 streams/writable-manywrites.js callback='no' writev='no' sync='no' n=40000000                    0.72 %       ±1.42% ±1.89% ±2.46%
 streams/writable-manywrites.js callback='no' writev='no' sync='yes' n=40000000          ***      2.82 %       ±0.54% ±0.72% ±0.94%
 streams/writable-manywrites.js callback='no' writev='yes' sync='no' n=40000000                   1.04 %       ±1.11% ±1.47% ±1.92%
 streams/writable-manywrites.js callback='no' writev='yes' sync='yes' n=40000000         ***      3.18 %       ±0.69% ±0.92% ±1.20%
 streams/writable-manywrites.js callback='yes' writev='no' sync='no' n=40000000                  -0.39 %       ±1.56% ±2.09% ±2.73%
 streams/writable-manywrites.js callback='yes' writev='no' sync='yes' n=40000000         ***      7.03 %       ±0.83% ±1.11% ±1.45%
 streams/writable-manywrites.js callback='yes' writev='yes' sync='no' n=40000000         ***      2.28 %       ±1.06% ±1.41% ±1.83%
 streams/writable-manywrites.js callback='yes' writev='yes' sync='yes' n=40000000        ***      8.46 %       ±0.89% ±1.18% ±1.55%

There is also a change to the benchmark runner to ensure that end() is not called multiple times. This was happening in the Writable benchmark and was at least causing weird display issues (e.g. improper fraction for # of configs, completion percentage bouncing back and forth, etc.) when using benchmark/compare.js and showing progress.

The reason why that was happening was that process.send() is used to send the result, which is async and gives individual benchmarks time to call .end() again before the process actually exits.

Checklist

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

[nodejs-github-bot]

CI: https://ci.nodejs.org/job/node-test-pull-request/28901/

[mcollina]

lgtm

[nodejs-github-bot]

CI: https://ci.nodejs.org/job/node-test-pull-request/28977/

[codebytere]

@mscdex this needs a manual backport to v13.x - if it shouldn't be feel free to just swap that label out for dont-land!