Platform mapping-based product config

This allows us to set product variables as build settings instead
of loading them from a target's provider, which further allows us
to read product config variables in transitions.

Bug: 287539062
Bug: 269577299
Test: Presubmits
Change-Id: I8497703f706162572ceb3486240e1eb02a37f5f6
diff --git a/android/test_config.go b/android/test_config.go
index 28d9ec4..2a59d92 100644
--- a/android/test_config.go
+++ b/android/test_config.go
@@ -35,7 +35,7 @@
 	envCopy["PATH"] = os.Getenv("PATH")
 
 	config := &config{
-		productVariables: productVariables{
+		productVariables: ProductVariables{
 			DeviceName:                          stringPtr("test_device"),
 			DeviceProduct:                       stringPtr("test_product"),
 			Platform_sdk_version:                intPtr(30),