Make it so that the indeterminate state of the checkbox matches the selected style

Create a module for array utilities.
Add a function that determines what amount of items in an array satisfy a condition

If only some of the hunks have been selected, display the file checkbox as indeterminate

Deduplicate and move the chunk utility into the array utilities module

Refactor and clean-up the component, so that the newer, more readable Svelte 5 state APIs are used

Rename the `Ownership` class to `SelectedOwnership`, as it is only used to determine the selected state of the files to add to a commit.

Renamed the methods as well to convey their actual purpose.

The `SelectedOwnership` class will be updated in a way that the selected is persisted across file/hunk ownership updates