module: keep ESM load cache entries in fast mode

[mcollina]

Keep per-URL load cache entries in fast-property mode while preserving their null prototype.

Median throughput from five alternating runs on matched Release builds (operations/s; higher is better):

Workload	Before	After	Change
Load-cache hit, 1 URL	48,976,708	99,289,555	+102.7%
Load-cache hit, 100 URLs	36,544,017	78,364,669	+114.4%
Repeated import, node:os	79,966	79,219	−0.9%
Repeated import, relative module	74,713	75,774	+1.4%
Cold imports, distinct data URLs	12,236	12,455	+1.8%

[nodejs-github-bot]

Review requested:

• @nodejs/loaders
• @nodejs/performance

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 90.33%. Comparing base (e7d8ab5) to head (da595c3).
⚠️ Report is 20 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #66276      +/-   ##
==========================================
+ Coverage   90.30%   90.33%   +0.03%     
==========================================
  Files         789      790       +1     
  Lines      272880   273835     +955     
  Branches    52110    52370     +260     
==========================================
+ Hits       246418   247375     +957     
- Misses      16912    16923      +11     
+ Partials     9550     9537      -13     

Files with missing lines	Coverage Δ
lib/internal/modules/esm/module_map.js	98.48% <100.00%> (+0.01%)	⬆️

... and 47 files with indirect coverage changes

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