events: use indexed appends in eventNames

[rozzilla]

Use indexed appends when collecting active names in EventEmitter.eventNames(), avoiding a primordial push call per name. Key ordering and filtering of removed listeners remain unchanged.

Local benchmarks on Apple M2/macOS with V8 15.6 show higher throughput:

• Repeated reads with 32-name fixtures: +9.6-12.6%.
• Add/read/remove cycles with 32-name fixtures: +8.2-12.0%.
• Four-name mixed string/symbol add/read/remove cycles: +6.2%.

Across 26 cases and 3,120 samples, seven gains were confirmed in both comparison directions after Holm correction. No corrected-significant regressions were detected, including listener-read and emission controls.

[nodejs-github-bot]

Review requested:

• @nodejs/performance

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 90.51%. Comparing base (531d28f) to head (02452d8).
⚠️ Report is 6 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #66875      +/-   ##
==========================================
+ Coverage   90.49%   90.51%   +0.01%     
==========================================
  Files         797      797              
  Lines      278221   278252      +31     
  Branches    53462    53468       +6     
==========================================
+ Hits       251786   251857      +71     
+ Misses      16809    16768      -41     
- Partials     9626     9627       +1     

Files with missing lines	Coverage Δ
lib/events.js	99.60% <100.00%> (ø)

... and 29 files with indirect coverage changes

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