Optimize creating AssetManager further

[henriquegemignani]

• Loading Prime Remastered objects is slow (1+s of compiling code)
• Decoding the resources section of the PAK is slow
• Minor optmizations

Moves startup+AssetManager creation from 2.7s to 0.4s for me

[codecov]

Codecov Report

Patch coverage: 84.61% and project coverage change: -0.02% ⚠️

Comparison is base (b0563d7) 64.24% compared to head (5333fd4) 64.23%.
Report is 2 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #90      +/-   ##
==========================================
- Coverage   64.24%   64.23%   -0.02%     
==========================================
  Files          75       75              
  Lines        4945     4949       +4     
==========================================
+ Hits         3177     3179       +2     
- Misses       1768     1770       +2     

Files Changed	Coverage Δ
src/retro_data_structures/formats/pak_wiiu.py	43.75% <ø> (ø)
src/retro_data_structures/formats/room.py	50.44% <0.00%> (-1.35%)	⬇️
src/retro_data_structures/asset_manager.py	67.14% <100.00%> (-0.19%)	⬇️
src/retro_data_structures/formats/pak_gc.py	93.97% <100.00%> (+0.38%)	⬆️

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