artifacts from earlier scans persist in library

[brainchild0]

Actual behaviour

If files are altered in a directory previously scanned, then new items may be added to the library, but altered ones are not fully cleared.

Expected behaviour

Scanning a directory should clear all the items in the library previously added from scanning the directory.

Or, the interface should save a list of library folders, which the user may request be scanned again, to regenerate all or part of the library.

Steps to reproduce

1. Scan a collection of album tracks as audio files in a directory.
2. Change an essential feature of some of the file metadata, such as disc number or total disc count.
3. Scan the same collection again.

The library may represent some of the albums multiple times, with some unable to play successfully.

Environment

Android version: 9
Device model: Nexus 5
Stock or customized system: Resurrection Remix custom build
Music-Player app version: 1.3.3