Problem/Motivation
This issue is spun off from #3038254-60: Delegate media library access to the "thing" that opened the library.
The MediaLibraryState object is the crucial link in the way the Media Library system is stitched together. It is used for access checking, selection handling, and the construction of the Media Library UI itself. For all these reasons, it makes sense for it to be able to influence caching, but currently it does not carry any caching information.
Proposed resolution
Implement CacheableDependencyInterface, and its accompanying trait, on MediaLibraryState.
Remaining tasks
Do that.
User interface changes
None.
API changes
None, really.
Data model changes
None.
Release notes snippet
Probably none. This is a change to internal plumbing.