List of installed files for each APEX is dist'ed

For each APEX, <apexname>-installed-files.txt is dist'ed to show the
list of files and their sizes that are included in the APEX.

Bug: 147605944
Test: m dist and examine the txt files

Change-Id: I565479523e51280fc88d5fbf8ea3f48ac0ae9fee

apex/apex.go

@@ -547,6 +547,8 @@ type apexBundle struct {
 	// Suffix of module name in Android.mk
 	// ".flattened", ".apex", ".zipapex", or ""
 	suffix string
+
+	installedFilesFile android.WritablePath
 }
 
 func addDependenciesForNativeModules(ctx android.BottomUpMutatorContext,