ffi: validate DynamicLibrary getter receivers

[trivikr]

Fixes: #65287

Check the receivers of the path, symbols, and functions getters before unwrapping them. This prevents incompatible receivers from crashing the process and makes the getters throw ERR_INVALID_THIS instead.

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Assisted-by: codex:gpt-5.6-sol

[nodejs-github-bot]

Review requested:

• @nodejs/ffi

[codecov]

Codecov Report

❌ Patch coverage is 81.25000% with 3 lines in your changes missing coverage. Please review.
✅ Project coverage is 90.32%. Comparing base (91a99c5) to head (5768e16).
⚠️ Report is 5 commits behind head on main.

Files with missing lines	Patch %	Lines
src/node_ffi.cc	81.25%	0 Missing and 3 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #65288      +/-   ##
==========================================
- Coverage   90.32%   90.32%   -0.01%     
==========================================
  Files         751      751              
  Lines      250000   249972      -28     
  Branches    47231    47227       -4     
==========================================
- Hits       225816   225784      -32     
- Misses      15566    15569       +3     
- Partials     8618     8619       +1     

Files with missing lines	Coverage Δ
src/node_ffi.cc	71.05% <81.25%> (+0.31%)	⬆️

... and 26 files with indirect coverage changes

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