Treat system_ext as system container

Bug: b/365135457
Test: m
Change-Id: Ic8fd60c0e1045f190b6608931ca1d65a784026f0
diff --git a/android/aconfig_providers.go b/android/aconfig_providers.go
index cb88e01..d2a9622 100644
--- a/android/aconfig_providers.go
+++ b/android/aconfig_providers.go
@@ -233,7 +233,8 @@
 	} else if m.ProductSpecific() {
 		container = "product"
 	} else if m.SystemExtSpecific() {
-		container = "system_ext"
+		// system_ext and system partitions should be treated as one container
+		container = "system"
 	}
 
 	paths = append(paths, aconfigFiles[container]...)