Add fieldtrial config for SmartDimNewMlAgent

Adding config before experiment/rollout to Stable in M84.
Modify the experiments to support multiarm groups.

Bug: 1067048
Change-Id: I90b3d9db7faacf939ae4c85d094e2961c01005dd
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2322146
Auto-Submit: Xinglong Luan <alanlxl@chromium.org>
Commit-Queue: Xinglong Luan <alanlxl@chromium.org>
Reviewed-by: Andrew Moylan <amoylan@chromium.org>
Reviewed-by: Ilya Sherman <isherman@chromium.org>
Cr-Commit-Position: refs/heads/master@{#792591}

testing/variations/fieldtrial_testing_config.json

@@ -6663,10 +6663,23 @@
             ],
             "experiments": [
                 {
-                    "name": "Enabled_20200609",
+                    "name": "EnabledWithExperimentalVersion_20200728",
+                    "params": {
+                        "smart_dim_experimental_version": "20200601.1"
+                    },
                     "enable_features": [
+                        "SmartDimExperimentalComponent",
                         "SmartDimNewMlAgent"
                     ]
+                },
+                {
+                    "name": "EnabledWithDefaultVersion_20200728",
+                    "enable_features": [
+                        "SmartDimNewMlAgent"
+                    ],
+                    "disable_features": [
+                        "SmartDimExperimentalComponent"
+                    ]
                 }
             ]
         }