Remove custom BackgroundThread and HandlerExecutor

Use stand-alone modules-utils library.
Files import has changed accordingly.

local filegroup has been updated to java_library.

Bug: 198418216
Tag: #refactor
Test: atest MediaProviderTests MediaProviderClientTests
Ignore-AOSP-First: Merge conflict resolution
Merged-In: Ie77277cd990216ba6cf6b83885574223e0fca590
Change-Id: Ie77277cd990216ba6cf6b83885574223e0fca590
11 files changed