feat(map): move map loading into worker

[fallenoak]

Similar to #30 and #32, this PR moves map and map area loading into a worker. Since map areas can be upwards of 1MiB on the large end, this significantly reduces the impact map loading has on frame rates.

This PR also eliminates the dedicated terrain manager in favor of one tied (more appropriately) to the map manager. Terrain is a component of map files, not a discrete model format like models (.m2) or map objects (.wmo).

Finally, as a result of the previous PRs introducing the loader pattern, this PR eliminates the old FormatManager and legacy SceneWorker classes.

[codecov-commenter]

Codecov Report

Attention: 166 lines in your changes are missing coverage. Please review.

Comparison is base (5f8340b) 10.24% compared to head (826d6a6) 10.27%.

Files	Patch %	Lines
src/lib/map/loader/util.ts	0.00%	73 Missing and 2 partials ⚠️
src/lib/map/loader/MapLoaderWorker.ts	0.00%	41 Missing and 5 partials ⚠️
src/lib/map/terrain/TerrainManager.ts	0.00%	24 Missing and 2 partials ⚠️
src/lib/map/MapManager.ts	0.00%	8 Missing ⚠️
src/lib/map/loader/MapLoader.ts	0.00%	8 Missing ⚠️
src/lib/map/DoodadManager.ts	0.00%	1 Missing ⚠️
src/lib/map/loader/const.ts	0.00%	1 Missing ⚠️
src/lib/map/loader/worker.ts	0.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #33      +/-   ##
==========================================
+ Coverage   10.24%   10.27%   +0.02%     
==========================================
  Files          44       40       -4     
  Lines        1483     1480       -3     
  Branches      270      265       -5     
==========================================
  Hits          152      152              
- Misses       1161     1162       +1     
+ Partials      170      166       -4     

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