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
diff --git a/android/soong_config_modules_test.go b/android/soong_config_modules_test.go
index 9677f34..b1810b3 100644
--- a/android/soong_config_modules_test.go
+++ b/android/soong_config_modules_test.go
@@ -175,7 +175,7 @@
 			},
 		}
 
-		ctx := NewTestContext()
+		ctx := NewTestContext(config)
 		ctx.RegisterModuleType("soong_config_module_type_import", soongConfigModuleTypeImportFactory)
 		ctx.RegisterModuleType("soong_config_module_type", soongConfigModuleTypeFactory)
 		ctx.RegisterModuleType("soong_config_string_variable", soongConfigStringVariableDummyFactory)
@@ -183,7 +183,7 @@
 		ctx.RegisterModuleType("test_defaults", soongConfigTestDefaultsModuleFactory)
 		ctx.RegisterModuleType("test", soongConfigTestModuleFactory)
 		ctx.PreArchMutators(RegisterDefaultsPreArchMutators)
-		ctx.Register(config)
+		ctx.Register()
 
 		_, errs := ctx.ParseBlueprintsFiles("Android.bp")
 		FailIfErrored(t, errs)