Convert RRO enforcement to transition mutator

Convert propagateRROEnforcementMutator to a transition mutator.

Bug: 367784740
Test: TestEnforceRRO_propagatesToDependencies
Test: TestAndroidResourceOverlays
Flag: EXEMPT refactor
Change-Id: I06c887f7203f3961f57bcaf458a191813e167561
diff --git a/java/rro_test.go b/java/rro_test.go
index 742c839..4d79130 100644
--- a/java/rro_test.go
+++ b/java/rro_test.go
@@ -282,7 +282,7 @@
 			enforceRROTargets: []string{"foo"},
 			rroDirs: map[string][]string{
 				"foo": {"product/vendor/blah/overlay/lib2/res"},
-				"bar": {"product/vendor/blah/overlay/lib2/res"},
+				"bar": nil,
 			},
 		},
 	}