Add enforcement of overlayable targetName

Adds android:targetName to the overlay manifest attributes and
PackageParser reads the name into PackageInfo. Specifying
android:targetName on an overlay allows the overlay to be associated
with a particular set of overlayable resources. The overlay can only
override the values of the resources defined within the target
overlayable element.

Test: idmap2_tests
Bug: 119390855
Bug: 110869880

Change-Id: I1128274af4cae983f61ae15cdfcbface63233ff2