Move playlist tests to a separate test file

These tests were originally added in ModernMediaScannerTest and they are
not related to ModernMediaScanner. Hence, moved them to a different
file.

Bug: 178007923
Test: atest com.android.providers.media.ResolvePlaylistTest
Change-Id: Ib4c4bda75e98a01709eeffd97b1a3a51540dc62a
Merged-In: Ib4c4bda75e98a01709eeffd97b1a3a51540dc62a
(cherry picked from commit 6dc8f64f318e3b405d8e5ecae4d5f4694418760e)
2 files changed