fs: reduce glob section allocations

[rozzilla]

Store non-globstar prefix counts in section records instead of a separate vector, avoiding its allocations during multi-globstar matching. Matching bounds use the same counts; matching behavior and recursion limits are unchanged. Add regression coverage and benchmarks for multi-globstar matching and in-memory path filtering.

Measured against ea6ec93 on Apple M2, macOS arm64, Node v27.0.0-pre, V8 15.5.35.22-node.15.

Filtering throughput changes below include unadjusted 95% confidence-interval half-widths. Reverse runs swap baseline and candidate labels.

Pattern	Path syntax	Candidate vs baseline	Reverse: baseline vs candidate
**/node_modules/**/test/**	POSIX	+26.57% +/- 1.33%	-20.81% +/- 1.04%
**/src/**	POSIX	+11.52% +/- 1.10%	-9.63% +/- 2.40%
**/node_modules/**/test/**	Windows	+18.36% +/- 1.47%	-15.96% +/- 1.19%
**/src/**	Windows	+12.52% +/- 1.82%	-10.44% +/- 1.64%

The 16 multi-globstar hit/miss microbenchmarks improve 18.73-37.88% in the forward comparison, with every gain confirmed in reverse.

Across 30 configurations, each direction used 30 independent samples per binary: 3,600 samples total. All 20 targeted gains remain significant after Holm correction in both directions; neither direction shows a corrected-significant regression.

[nodejs-github-bot]

Review requested:

• @nodejs/path
• @nodejs/performance

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 90.48%. Comparing base (3f0c2e4) to head (60d8a41).
⚠️ Report is 5 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main   #66716   +/-   ##
=======================================
  Coverage   90.48%   90.48%           
=======================================
  Files         791      791           
  Lines      277204   277210    +6     
  Branches    53309    53317    +8     
=======================================
+ Hits       250827   250833    +6     
- Misses      16789    16805   +16     
+ Partials     9588     9572   -16     

Files with missing lines	Coverage Δ
src/glob/glob_matcher.cc	66.86% <100.00%> (+0.06%)	⬆️

... and 31 files with indirect coverage changes

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[mcollina]

lgtm