perf: limit the number of concurrently open file watchers on macOS

[chenjiahan]

Limit the number of concurrently open file watchers on macOS to 20 to make FSWatcher.close faster.

Related PRs:

• Add WATCHPACK_WATCHER_LIMIT=20 vercel/next.js#51826
• Limit the number of concurrently open file watchers on macos vercel/next.js#73741
• perf: set default WATCHPACK_WATCHER_LIMIT to 20 web-infra-dev/rspack#5486 (We tried setting WATCHPACK_WATCHER_LIMIT by default in the Rspack CLI, but I found that this did not work because watchpack was loaded earlier than the WATCHPACK_WATCHER_LIMIT was set in the Rspack CLI)

Related issues:

• watchpack blocks for a long time closing FSWatchers on osx #222
• FSWatcher.close() incurs a big performance cost in >=10.16 nodejs/node#29949

[alexander-akait]

I am fine with it, but can we add a test case/simple perf case to verify it and to avoid future regressions?

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 91.46%. Comparing base (33df387) to head (e3426af).
Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #249      +/-   ##
==========================================
- Coverage   92.20%   91.46%   -0.75%     
==========================================
  Files           6        6              
  Lines        1065     1066       +1     
  Branches      258      258              
==========================================
- Hits          982      975       -7     
- Misses         83       91       +8     

Flag	Coverage Δ
integration	91.46% <100.00%> (-0.75%)	⬇️

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[chenjiahan]

Sure, creating a stable perf test seems difficult, so I added a simple test to check the watcher limit value

[alexander-akait]

@chenjiahan very weird, looks like Node.js@22 has regression somewhere on windows... I know it is not related to these changes... I will look deeply

[alexander-akait]

@chenjiahan sorry for delay, can you rebase?

[alexander-akait]

We fixed problem with node@22

[chenjiahan]

Rebased 😄