Fix TemporaryFileManager not deleting directories correctly

[Al12rs]

fixes Nexus-Mods/NexusMods.App#904

When adding the test I found that the InMemoryFS was throwing when deleting the folder recursively, so fixed that as well.

[codecov-commenter]

Codecov Report

Attention: 5 lines in your changes are missing coverage. Please review.

Comparison is base (ab2d282) 87.19% compared to head (d19fd49) 86.94%.

Files	Patch %	Lines
...straction/InMemoryFileSystem/InMemoryFileSystem.cs	72.22%	4 Missing and 1 partial ⚠️

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Additional details and impacted files

@@            Coverage Diff             @@
##             main      #36      +/-   ##
==========================================
- Coverage   87.19%   86.94%   -0.25%     
==========================================
  Files          42       42              
  Lines        3123     3148      +25     
  Branches      537      542       +5     
==========================================
+ Hits         2723     2737      +14     
- Misses        343      347       +4     
- Partials       57       64       +7     

Flag	Coverage Δ
Linux	?
Windows	86.94% <81.48%> (+0.13%)	⬆️
macOS	?

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