Split iIMDShape, separate game state data from display data, + initial graphics overrides support

[past-due]

Note
Requires: #3307

This draft PR implements several key core changes:

1. Split iIMDShape, separate game state data from display data
   • iIMDBaseShape is the base data that can be safely used for game state calculations, and is always derived from the base model data. It contains a pointer to the display iIMDShape data (used for display purposes only), which may be loaded from a different place (i.e. graphics overrides).
2. Support tileset TEXTURE overrides in PIE 4
3. Basic under-the-hood support for new "graphics overrides" support
4. Refactoring of how textures are compressed as part of the build process

Graphics Overrides

This PR implements the basics to support graphics overrides.

The goal: Use the same (base) game data for all game state calculations / the simulation, but support using a different set of data for rendering / display purposes.

Use-case: To allow future bundling of ARMod / high quality models, and allow players to play versus each other while independently deciding whether to use classic, normal, or ARMod/HQ models for the visual appearance of the game.

To test this right now:

• Extract ARMod, and place in <config dir>/graphics_overrides/curr (this may change before this PR is ultimately ready for merging)
  • This should cause ARMod models and textures to be rendered, however all game state calculations should use data extracted from the base (default) models.

Future TODOs (in a subsequent PR):

• Similar to terrain overrides, provide configuration in Options (and enumeration of graphics_overrides). (Presumably allow these to be packaged, like terrain overrides?)