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/androidmk_test.go b/android/androidmk_test.go
index 0bb455b..940e324 100644
--- a/android/androidmk_test.go
+++ b/android/androidmk_test.go
@@ -47,8 +47,8 @@
 	config.inMake = true // Enable androidmk Singleton
 
 	ctx := NewTestContext()
-	ctx.RegisterSingletonType("androidmk", SingletonFactoryAdaptor(AndroidMkSingleton))
-	ctx.RegisterModuleType("custom", ModuleFactoryAdaptor(customModuleFactory))
+	ctx.RegisterSingletonType("androidmk", AndroidMkSingleton)
+	ctx.RegisterModuleType("custom", customModuleFactory)
 	ctx.Register()
 
 	bp := `