[devicelab] Enable a LUCI try builder. (#64004)

dev/devicelab/manifest.yaml

@@ -98,7 +98,6 @@ tasks:
       Gallery for iOS from Mac.
     stage: devicelab_ios
     required_agent_capabilities: ["mac/ios"]
-    on_luci: true
 
   flutter_gallery_win__compile:
     description: >
@@ -467,6 +466,7 @@ tasks:
       Builds an obfuscated app and verifies contents and structure
     stage: devicelab
     required_agent_capabilities: ["mac/ios"]
+    on_luci: true
 
   tiles_scroll_perf_ios__timeline_summary:
     description: >

dev/try_builders.json

@@ -79,10 +79,16 @@
          "enabled":true
       },
       {
-         "name": "Windows tool_tests",
-         "repo": "flutter",
-         "task_name": "win_tool_tests",
-         "enabled":true
+        "name": "Windows tool_tests",
+        "repo": "flutter",
+        "task_name": "win_tool_tests",
+        "enabled":true
+      },
+      {
+        "name": "testonly_devicelab_tests",
+        "repo": "flutter",
+        "taskName": "testonly_devicelab_tests",
+        "enabled": true
       }
    ]
 }