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

android/package_test.go

@@ -86,9 +86,9 @@ func testPackage(fs map[string][]byte) (*TestContext, []error) {
 	// Create a new config per test as visibility information is stored in the config.
 	config := TestArchConfig(buildDir, nil, "", fs)
 
-	ctx := NewTestArchContext()
+	ctx := NewTestArchContext(config)
 	RegisterPackageBuildComponents(ctx)
-	ctx.Register(config)
+	ctx.Register()
 
 	_, errs := ctx.ParseBlueprintsFiles(".")
 	if len(errs) > 0 {