permission: add --allow-env flag for environment variable access control

[nabeel378]

Adds --allow-env permission flag to control access to environment
variables when the permission model is enabled (--permission).

Supported usage:

• --allow-env — grants access to all environment variables
• --allow-env=HOME,PATH — grants access only to specified variables

When --permission is enabled without --allow-env, all calls to
process.env will throw ERR_ACCESS_DENIED.

Fixes: #62424

[nodejs-github-bot]

Review requested:

• @nodejs/config
• @nodejs/gyp
• @nodejs/security-wg

[codecov]

Codecov Report

❌ Patch coverage is 89.06250% with 7 lines in your changes missing coverage. Please review.
✅ Project coverage is 89.55%. Comparing base (58a8e1d) to head (b6a89cf).
⚠️ Report is 2 commits behind head on main.

Files with missing lines	Patch %	Lines
src/node_env_var.cc	87.09%	0 Missing and 4 partials ⚠️
src/permission/env_var_permission.cc	85.00%	1 Missing and 2 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #62827      +/-   ##
==========================================
- Coverage   89.69%   89.55%   -0.14%     
==========================================
  Files         706      708       +2     
  Lines      218222   218931     +709     
  Branches    41768    41881     +113     
==========================================
+ Hits       195731   196065     +334     
- Misses      14411    14745     +334     
- Partials     8080     8121      +41     

Files with missing lines	Coverage Δ
lib/internal/process/permission.js	83.87% <100.00%> (-16.13%)	⬇️
src/env.cc	85.12% <100.00%> (-0.34%)	⬇️
src/node_options.cc	76.53% <100.00%> (+0.02%)	⬆️
src/node_options.h	97.98% <ø> (ø)
src/permission/env_var_permission.h	100.00% <100.00%> (ø)
src/permission/permission.cc	81.92% <100.00%> (+0.33%)	⬆️
src/permission/permission.h	100.00% <ø> (ø)
src/permission/env_var_permission.cc	85.00% <85.00%> (ø)
src/node_env_var.cc	82.08% <87.09%> (-0.13%)	⬇️

... and 68 files with indirect coverage changes

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