src: let embedders exempt linked bindings from the addon permission

[codebytere]

Refs: #65432

Since #65432 process._linkedBinding() is subject to the permission model's addon scope, the same as process.dlopen(). A stock node binary has no linked bindings, so this only affects embedders, and for an embedder that implements part of its runtime as linked bindings (NODE_LINKED_MODULE / node::AddLinkedBinding()) it means its own bootstrap cannot reach them under --permission unless the user also passes --allow-addons - which then allows loading addons from the file system as well.

This adds EnvironmentFlags::kNoAddonPermissionForLinkedBindings. When an embedder sets it, GetLinkedBinding() skips the addon permission check for that Environment and the worker threads it creates; process.dlopen() stays gated by --allow-addons and the default behavior is unchanged. The reasoning is that --allow-addons guards loading native code from disk at runtime, while linked bindings are compiled into the executable by the embedder and trusted the same way the built-in bindings are.

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Disclosure: the code, tests and this description were written by Claude Code, directed and reviewed by @codebytere.

[codecov]

Codecov Report

❌ Patch coverage is 50.00000% with 4 lines in your changes missing coverage. Please review.
✅ Project coverage is 90.26%. Comparing base (67e66b8) to head (eee9f6c).

Files with missing lines	Patch %	Lines
src/node_worker.cc	0.00%	2 Missing and 1 partial ⚠️
src/node_binding.cc	66.66%	0 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #66067      +/-   ##
==========================================
- Coverage   90.27%   90.26%   -0.01%     
==========================================
  Files         789      789              
  Lines      271473   271480       +7     
  Branches    51808    51815       +7     
==========================================
- Hits       245066   245064       -2     
- Misses      16880    16885       +5     
- Partials     9527     9531       +4     

Files with missing lines	Coverage Δ
src/env-inl.h	93.95% <100.00%> (+0.02%)	⬆️
src/env.h	97.26% <ø> (ø)
src/node.h	91.66% <ø> (ø)
src/node_binding.cc	70.79% <66.66%> (+0.16%)	⬆️
src/node_worker.cc	82.05% <0.00%> (-0.05%)	⬇️

... and 27 files with indirect coverage changes

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