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/compliance/notice_test.go b/compliance/notice_test.go
index 6187e53..e8578ec 100644
--- a/compliance/notice_test.go
+++ b/compliance/notice_test.go
@@ -35,4 +35,4 @@
 
 	m := result.Module("notice_xml_system", "android_arm64_armv8-a").(*NoticeXmlModule)
 	android.AssertStringEquals(t, "output file", "NOTICE.xml.gz", m.outputFile.Base())
-}
\ No newline at end of file
+}