esm: optimize string checks and slicing with direct index access

[mertcanaltin]

Optimize string manipulation by replacing prototype methods with direct index access for improved performance.

[nodejs-github-bot]

Review requested:

• @nodejs/loaders

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 2 lines in your changes missing coverage. Please review.

Project coverage is 88.40%. Comparing base (4d6d7d6) to head (5b77adb).
Report is 9 commits behind head on main.

Files with missing lines	Patch %	Lines
lib/internal/modules/esm/fetch_module.js	0.00%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #55435      +/-   ##
==========================================
- Coverage   88.40%   88.40%   -0.01%     
==========================================
  Files         653      653              
  Lines      187604   187602       -2     
  Branches    36119    36114       -5     
==========================================
- Hits       165849   165843       -6     
+ Misses      14983    14977       -6     
- Partials     6772     6782      +10     

Files with missing lines	Coverage Δ
lib/internal/modules/esm/fetch_module.js	43.00% <0.00%> (-0.38%)	⬇️

... and 27 files with indirect coverage changes

[legendecas]

This is also done in #55407.

[mertcanaltin]

This is also done in #55407.

I'm closing this thank you very much