OverlayManagerImpl support to commit OverlayManagerTransaction

The major task of OverlayManagerImpl is to create not only a frro
file but also an idmap file for a FabricatedOverlay instance. The
app attaches multiple FabricatedOverlay instances into an
OverlayManagerTransaction.

This patch makes OverlayManagerImpl process multiple requests in the
OverlayManagerTransaction in one commitment.

Test: atest \
          OverlayHostTests \
          OverlayDeviceTests \
          SelfTargetingOverlayDeviceTests \
          OverlayRemountedTest \
          FrameworksServicesTests:com.android.server.om \
          CtsContentTestCases:android.content.om.cts \
          idmap2_tests

Bug: 205919743
Change-Id: I22e45fb6b3935cea4b24038dbd82d84bc9ca7db3