Add actor and name parsing for overlayable

Add parsing of two overlayable attributes:
 name : The unnique identifying name of the overlayable set of resources
 actor: The component responsible for enabling and disabling overlays
        targeting the specified set of resources

Bug: 110869880
Bug: 119390855
Test: m -j aapt2_tests
Change-Id: Id42463e2b92b69034fb39cd29bc8606affb61ba7