Remove unused TopDownMutatorContext methods

Remove methods on TopDownMutatorContext that are no longer used.
This deletes everything unique to BaseMutatorContext, so delete that
too and replace it with BaseModuleContext.

Bug: 367784740
Test: builds
Flag: EXEMPT refactor
Change-Id: Id37c7b7e3d46d75afaf7752862b08f766217f08b
diff --git a/android/arch.go b/android/arch.go
index 1ec971d..e2d0d0d 100644
--- a/android/arch.go
+++ b/android/arch.go
@@ -1369,7 +1369,7 @@
 
 // Returns the structs corresponding to the properties specific to the given
 // architecture and OS in archProperties.
-func getArchProperties(ctx BaseMutatorContext, archProperties interface{}, arch Arch, os OsType, nativeBridgeEnabled bool) []reflect.Value {
+func getArchProperties(ctx BaseModuleContext, archProperties interface{}, arch Arch, os OsType, nativeBridgeEnabled bool) []reflect.Value {
 	result := make([]reflect.Value, 0)
 	archPropValues := reflect.ValueOf(archProperties).Elem()