Rename product_services to system_ext

Bug: 134359158
Test: build and check if system_ext.img is created
Change-Id: Ice3229baf97a94c24a6eea22e7d4571941d7f843

android/paths.go

@@ -1145,8 +1145,8 @@ func modulePartition(ctx ModuleInstallPathContext) string {
 		partition = ctx.DeviceConfig().OdmPath()
 	} else if ctx.ProductSpecific() {
 		partition = ctx.DeviceConfig().ProductPath()
-	} else if ctx.ProductServicesSpecific() {
-		partition = ctx.DeviceConfig().ProductServicesPath()
+	} else if ctx.SystemExtSpecific() {
+		partition = ctx.DeviceConfig().SystemExtPath()
 	} else {
 		partition = "system"
 	}