refactor(client-fs): asset storage and path handling

[arse09]

This pr is meant for updating the current asset and installation directory layout to prepare for #62.

Summary

• Added supported versions check
• data.rs now is dirs.rs and it stores the paths for the directories that the client uses
• Replaced ambiguous assets_dir variable with jar_assets_dir, objects_dir and indexes_dir. Also added pomc_assets_dir to store all custom non vanilla data.
• New directory layout, the client has access to the folders that are commented from the DataDirs struct stored in the App:

.pomc/
├── assets/
│   ├── indexes/                        # indexes_dir
│   └── objects/                        # objects_dir
├── pomc-assets/                        # pomc_assets_dir
├── versions/
│   └── 26.1/
│       ├── 26.1.jar
│       ├── 26.1.json
│       └── extracted/
│           └── assets/                 # jar_assets_dir
│               └── minecraft/
│                   ├── blockstates/
│                   ├── models/
│                   └── textures/
│
├── installations.json
└── installations/

<installation>/                         # game_dir
    ├── saves/
    ├── mods/
    ├── resourcepacks/
    ├── shaderpacks/
    ├── screenshots/
    ├── logs/
    ├── options.json
    ├── servers.json
    └── icon.png

Test plan

• Check that all assets are loaded correctly from their respective directories.

[Purdze]

Version is now a required arg, cargo run without --version will fail. Consider keeping it Option with a fallback or document that dev mode needs --version

for_each_blockstate dropped asset_index, blockstates now only resolve from jar_assets_dir. This is fine if blockstates are always in the extracted jar, but worth confirming no edge case uses the asset index for blockstate lookup

Might be worth checking settings.json doesnt collide with other settings

[arse09]

Block-states are always in the JAR, never in objects/ so there should not be any edge cases. Also, changed the settings.json to options.json so that it doesn't conflict with the settings.json from the launcher.