Support generating custom block mappings and resourcepacks

[eclipseisoffline]

This PR adds support for generating custom block mappings and bedrock resourcepacks to Rainbow. This is currently a work-in-progress and highly experimental: there are still many bugs and TO-DOs. However, the PR has already seem some success with basic custom blocks from Polymer mods like Polymer Patch Bundle (with blockus) and TSA: Concrete!.

The PR adds records and codecs for Geyser's block mappings, which are used by the new BedrockBlockMapper utility class, which turns overridden block states into a Geyser block mapping and appropriate geometry and texture files in the exported resourcepack. ModelTextures has been abstracted to support both textures for blocks and items: it has been split into ModelTextures and the new ItemModelTextures interface (which holds most of the old ModelTextures code for handling item textures). A new implementation of ModelTextures, BlockModelTextures, has been created for handling block textures.

Users will be able to manually map a single block state, by passing it as argument to a command or by passing the position of such a block state in the world to a command. Rainbow will also provide an option to automatically detect all custom block state overrides in the currently loaded resourcepacks (may not be perfect).

A short list of TO-DOs for this PR:

• Making sure block and item textures don't overlap.
• Proper UX (improve commands).
• Proper usage/mapping of the built-in full_block and cross geometry files.
  • full_block
  • cross
• Properly note statistics in report.txt (will require a rework of how statistics are passed through the code).
• Proper handling of some errors that can occur during converting (such as no materials).
• Improve automatic detection of custom block state overrides.
• Datagen module (needs a simple AssetResolver fix)