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/cc/genrule_test.go b/cc/genrule_test.go
index a366f76..0c7952b 100644
--- a/cc/genrule_test.go
+++ b/cc/genrule_test.go
@@ -22,9 +22,9 @@
 )
 
 func testGenruleContext(config android.Config) *android.TestContext {
-	ctx := android.NewTestArchContext()
+	ctx := android.NewTestArchContext(config)
 	ctx.RegisterModuleType("cc_genrule", genRuleFactory)
-	ctx.Register(config)
+	ctx.Register()
 
 	return ctx
 }