[Files] Implement files feature

[y9vad9]

TODO:

• Copy timers or users feature module and rename it to files, add modules to settings.gradle.kts
• Change dependencies in files submodules to files submodules instead of previous feature dependencies
• Write domain logic (use-case for uploading file, getting file, repository for it)
• Write tests for domain logic
• Implement data logic in data layer using our sdk.

Note
Probably, you don't even need to implement database logic (only if you will make special logic for caching), but you need to implement caching on disk using some multiplatform library like okio).

Use dev branch as head branch.