Update DownloadStorageProvider to include MediaStore.Downloads.

Bug: 120879205
Test: manual
Test: atest DownloadProviderTests
Test: atest cts/tests/app/src/android/app/cts/DownloadManagerTest.java
Test: atest MediaProviderTests
Test: atest cts/tests/tests/provider/src/android/provider/cts/MediaStore*
Change-Id: I44be836899437d87fc1a00e5fe316c6b68488643
5 files changed