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/rust/testing.go b/rust/testing.go
index 4001566..66877a9 100644
--- a/rust/testing.go
+++ b/rust/testing.go
@@ -127,8 +127,8 @@
 	return bp
 }
 
-func CreateTestContext() *android.TestContext {
-	ctx := android.NewTestArchContext()
+func CreateTestContext(config android.Config) *android.TestContext {
+	ctx := android.NewTestArchContext(config)
 	android.RegisterPrebuiltMutators(ctx)
 	ctx.PreArchMutators(android.RegisterDefaultsPreArchMutators)
 	cc.RegisterRequiredBuildComponentsForTest(ctx)