Conslidate @MainHandler and similar to @Main (and similar).

@MainHandler, @MainLooper, @MainResources -> @Main
@BgHandler, @BgLooper -> @Background.

Also, move the providers for Handlers and Loopers into the
ConcurrencyModule.

Bug: 146510722
Test: atest SystemUITests
Change-Id: I991735e1fdca397784427409a2ae696a7374f584
58 files changed