Add tests for bulkUpdateOemMetadataInNextScan

Added tests to verify correct permission checks happen for
bulkUpdateOemMetadataInNextScan. Since this API behavior depends on
implementation of OemMetadataService by OEMs, we cannot verify API
behavior in CTS.

Test: atest android.provider.cts.media.modern.MediaStore_FilesTest
Bug: 437815531
Flag: com.android.providers.media.flags.enable_oem_metadata_update
Change-Id: Ic9a4e390360727ea33b6c4c267bb0103f22305c9