Allow for overriding container packagename for an Apex.

Test: go test ./... -test.v -run TestOverrideApex
BUG: 148198056
Change-Id: If49042a7acbf9f0dcb505664863d97805902e459

apex/apex.go

@@ -1359,6 +1359,10 @@ type overridableProperties struct {
 
 	// Logging Parent value
 	Logging_parent string
+
+	// Apex Container Package Name.
+	// Override value for attribute package:name in AndroidManifest.xml
+	Package_name string
 }
 
 type apexPackaging int