Add FileManager to TiledDataset

[SolarDrew]

Does what it says on the tin. Addresses but doesn't necessarily close #244

[codspeed-hq]

CodSpeed Performance Report

Merging #437 will improve performances by 10.4%

_{Comparing SolarDrew:tiledds-improvements (795c4b6) with main (fb3ca0d)}

Summary

⚡ 1 improvements
✅ 8 untouched benchmarks

Benchmarks breakdown

	Benchmark	main	SolarDrew:tiledds-improvements	Change
⚡	test_generate_celestial	5.8 ms	5.3 ms	+10.4%

[SolarDrew]

Well I'm slightly confused and concerned by the 10% speed improvement to test_generate_celestial() because I didn't think I'd changed anything that would affect it...

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 96.71%. Comparing base (fb3ca0d) to head (795c4b6).

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #437      +/-   ##
==========================================
+ Coverage   96.69%   96.71%   +0.02%     
==========================================
  Files          68       68              
  Lines        4321     4352      +31     
==========================================
+ Hits         4178     4209      +31     
  Misses        143      143              

Flag	Coverage Δ
	42.89% <21.87%> (-0.15%)	⬇️

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