Add OutputFilesProvider support for singleton

This CL also changes to use OutputFilesProvider on rust module, which
has singleton involved.

Test: CI
Bug: 339477385
Bug: 348494466
Change-Id: Idc5c0fb9f8425f09184d5b73531ee3052e5a076c
diff --git a/rust/test_test.go b/rust/test_test.go
index 6d0ebcf..dc796c8 100644
--- a/rust/test_test.go
+++ b/rust/test_test.go
@@ -106,12 +106,9 @@
 
 	ctx := testRust(t, bp)
 
-	module := ctx.ModuleForTests("main_test", "android_arm64_armv8-a").Module()
-	testBinary := module.(*Module).compiler.(*testDecorator)
-	outputFiles, err := module.(android.OutputFileProducer).OutputFiles("")
-	if err != nil {
-		t.Fatalf("Expected rust_test to produce output files, error: %s", err)
-	}
+	testingModule := ctx.ModuleForTests("main_test", "android_arm64_armv8-a")
+	testBinary := testingModule.Module().(*Module).compiler.(*testDecorator)
+	outputFiles := testingModule.OutputFiles(t, "")
 	if len(outputFiles) != 1 {
 		t.Fatalf("expected exactly one output file. output files: [%s]", outputFiles)
 	}
@@ -168,12 +165,10 @@
  `
 
 	ctx := testRust(t, bp)
-	module := ctx.ModuleForTests("main_test", "android_arm64_armv8-a").Module()
+	testingModule := ctx.ModuleForTests("main_test", "android_arm64_armv8-a")
+	module := testingModule.Module()
 	testBinary := module.(*Module).compiler.(*testDecorator)
-	outputFiles, err := module.(android.OutputFileProducer).OutputFiles("")
-	if err != nil {
-		t.Fatalf("Expected rust_test to produce output files, error: %s", err)
-	}
+	outputFiles := testingModule.OutputFiles(t, "")
 	if len(outputFiles) != 1 {
 		t.Fatalf("expected exactly one output file. output files: [%s]", outputFiles)
 	}