GamePath FileTree support

[Al12rs]

closes #553

Adds support for GamePath based FileTrees (FileTreeNode<GamePath>).

• Made game path extend IPath<GamePath> so the file tree can use it.
• Implemented IPath<> interface methods
• Added tests for new methods
• Added simple test for FileTreeNode<GamePath> (Paths library has more extensive testing already).

[Al12rs]

Follow up to Nexus-Mods/NexusMods.Paths#11

[codecov]

Codecov Report

Merging #570 (410ef82) into main (42aeda6) will increase coverage by 67.54%.
Report is 5 commits behind head on main.
The diff coverage is 100.00%.

Additional details and impacted files

@@            Coverage Diff            @@
##           main     #570       +/-   ##
=========================================
+ Coverage      0   67.54%   +67.54%     
=========================================
  Files         0      602      +602     
  Lines         0    16226    +16226     
  Branches      0     1105     +1105     
=========================================
+ Hits          0    10960    +10960     
- Misses        0     4976     +4976     
- Partials      0      290      +290     

Flag	Coverage Δ
Linux	67.54% <100.00%> (?)
clean_environment_tests	67.54% <100.00%> (?)

Flags with carried forward coverage won't be shown. Click here to find out more.

Files Changed	Coverage Δ
src/NexusMods.DataModel/Games/GamePath.cs	94.73% <100.00%> (ø)

... and 601 files with indirect coverage changes