Split Documents&Other

Splitting Documents&Other category in
Settings > Storage into "Documents"
and "Other".

"Documents" category is calculated by
querying MediaStore for all files with
MediaType = "Document".

"Other" category is calculated by
querying MediaStore for all files with
MEDIA_TYPE != "Image" AND MEDIA_TYPE != "Video"
AND MEDIA_TYPE != "Audio" AND MEDIA_TYPE != "Document".

Bug: 328505030
Test: atest StorageItemPreferenceControllerTest
Test: atest StorageCacheHelperTest
Change-Id: I413c502c7b3fd66df9a3b5e0d91f8bd024f4b6e0