Expose resource roots

[Thom1729]

In order to implement ResourcePath.from_file_path() and Resource_path.file_path(), we internally keep a list of ResourceRoot objects. Exposing these roots could allow users to answer various tricky questions about resources:

• Is a given resource from a zipped or unzipped package?
• Does a given resource have overrides?
• When was a given resource last modified?

This functionality could be useful for packages like OverrideAudit. In addition, it could be used to implement resource caching (#24): a resource must be reloaded if either the modification time or the resource root has changed.

As a first thought, a resource root could support the following operations:

• resource_to_file_path(path) -> Path (already implemented)
• file_to_resource_path(path) -> ResourcePath (already implemented)
• resource_exists(path) → boolean
• resource_modified(path) → timestamp
• load_resource(path) → string
• load_binary_resource(path) → bytes

The following operation would be provided at the ResourcePath level (or perhaps in a new class?):

• roots_providing_resource(path) → List[ResourceRoot]

[FichteFoll]

Good idea, imo.