No-op refactor Item and Category column names

Refactored names to use the CloudMediaProviderContract API as source
of truth.

Test: atest ItemTest
Test: atest ItemsProviderTest
Test: atest CategoryTest
Test: atest PickerViewModelTest
Bug: 196071169
Change-Id: Ieb466fed0055dd9b4df40813f2b4878c57ea6eb8
Merged-In: Ieb466fed0055dd9b4df40813f2b4878c57ea6eb8
(cherry picked from commit a541ef7cd1d5b8cd4b927effbb4fd87e83de204f)
9 files changed