options: Add support for path using std::filesystem::path

[mwestphal]

• Add a _option_variant_convert logic in f3dOptions.cmake for conversion from an option type to a variant type
• Add path aka std::filesystem::path has a valid option type
• Add parse/format for path
• Use path for hdri.file, font_file, all texture options
• Add functionnal, unit and coverage testing
• Add doc
• Added deprecation code for collapse behavior

related to #1570

[github-actions]

You are modifying libf3d public API! ⚠️Please update bindings accordingly⚠️!
You can find them in their respective directories: python, java, webassembly.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 95.80%. Comparing base (9d5bc10) to head (dfd2db9).

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #2046      +/-   ##
==========================================
+ Coverage   95.79%   95.80%   +0.01%     
==========================================
  Files         128      128              
  Lines       10485    10499      +14     
==========================================
+ Hits        10044    10059      +15     
+ Misses        441      440       -1     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.
• 📦 JS Bundle Analysis: Save yourself from yourself by tracking and limiting bundle sizes in JS merges.

[mwestphal]

Im not convinced by my doc here but I also do not know if I should be super specific.