Create `cache-metadata-android` and `cache-preview-android` components

The `arklib-android` repo contains cache-generating pipeline which should be decoupled from the core since it's optional.

It has 3 main parts:
- [Abstract "Processor" classes](https://github.com/ARK-Builders/arklib-android/tree/main/lib/src/main/java/dev/arkbuilders/arklib/data/processor)
- [Metadata extraction](https://github.com/ARK-Builders/arklib-android/tree/main/lib/src/main/java/dev/arkbuilders/arklib/data/metadata)
- [Previews and thumbnails generation](https://github.com/ARK-Builders/arklib-android/tree/main/lib/src/main/java/dev/arkbuilders/arklib/data/preview)

The codebase needs some refactoring, too.

Start by reviewing the three linked areas: lib/src/main/java/dev/arkbuilders/arklib/data/processor, data/metadata, and data/preview. Map how the cache-generating pipeline depends on the core and determine the component boundaries needed for cache-metadata-android and cache-preview-android. Done means the optional cache pipeline is decoupled from the core and the refactoring scope is addressed.

Written by the indexing model from the issue text.