Pass Config to NewTestContext instead of ctx.Register

Prepare for using Config when adding singletons by passing
Config to NewTestContext and NewContext instead of to ctx.Register.
This will enable a followup change to store SingletonMakeVarsProviders
registered on the Context in the Config, which is necessary to run
multiple tests in parallel without data races.

Test: all soong tests
Change-Id: Id229629a4e42ff4487d317241673837726c075fc

xml/xml_test.go

@@ -57,10 +57,10 @@ func testXml(t *testing.T, bp string) *android.TestContext {
 		"baz.xml": nil,
 	}
 	config := android.TestArchConfig(buildDir, nil, bp, fs)
-	ctx := android.NewTestArchContext()
+	ctx := android.NewTestArchContext(config)
 	ctx.RegisterModuleType("prebuilt_etc", etc.PrebuiltEtcFactory)
 	ctx.RegisterModuleType("prebuilt_etc_xml", PrebuiltEtcXmlFactory)
-	ctx.Register(config)
+	ctx.Register()
 	_, errs := ctx.ParseFileList(".", []string{"Android.bp"})
 	android.FailIfErrored(t, errs)
 	_, errs = ctx.PrepareBuildActions(config)