Make TestContext.RegisterModuleType take an android.ModuleFactory

Avoid having to pass ModuleFactoryAdaptor to every call to
RegisterModuleType in a test by wrapping RegisterModuleType.

Test: all soong tests
Change-Id: If8847d16487de0479cc3020b728256922b3cadba
diff --git a/android/variable_test.go b/android/variable_test.go
index c1910fe..1826e39 100644
--- a/android/variable_test.go
+++ b/android/variable_test.go
@@ -159,17 +159,17 @@
 func TestProductVariables(t *testing.T) {
 	ctx := NewTestContext()
 	// A module type that has a srcs property but not a cflags property.
-	ctx.RegisterModuleType("module1", ModuleFactoryAdaptor(testProductVariableModuleFactoryFactory(struct {
+	ctx.RegisterModuleType("module1", testProductVariableModuleFactoryFactory(struct {
 		Srcs []string
-	}{})))
+	}{}))
 	// A module type that has a cflags property but not a srcs property.
-	ctx.RegisterModuleType("module2", ModuleFactoryAdaptor(testProductVariableModuleFactoryFactory(struct {
+	ctx.RegisterModuleType("module2", testProductVariableModuleFactoryFactory(struct {
 		Cflags []string
-	}{})))
+	}{}))
 	// A module type that does not have any properties that match product_variables.
-	ctx.RegisterModuleType("module3", ModuleFactoryAdaptor(testProductVariableModuleFactoryFactory(struct {
+	ctx.RegisterModuleType("module3", testProductVariableModuleFactoryFactory(struct {
 		Foo []string
-	}{})))
+	}{}))
 	ctx.PreDepsMutators(func(ctx RegisterMutatorsContext) {
 		ctx.BottomUp("variable", variableMutator).Parallel()
 	})