added new dynamic nn file

Project/Assets/ML-Agents/Examples/Walker/Prefabs/WalkerPairDynamic.prefab

         type: 3}
       propertyPath: m_Model
       value: 
-      objectReference: {fileID: 11400000, guid: 8b4174e75a11c4f0eb5958c04eeab1d1,
+      objectReference: {fileID: 11400000, guid: e1adbf3a9d04441259d6327d42fcce3d,
         type: 3}
     - target: {fileID: 5756232957735828584, guid: 80520f477184d46c8841239b4a818a3e,
         type: 3}

Project/Assets/ML-Agents/Examples/Walker/Scripts/WalkerAgentDynamic.cs

     {
         m_ChestRb.mass = m_ResetParams.GetWithDefault("chest_mass", 8);
         m_SpineRb.mass = m_ResetParams.GetWithDefault("spine_mass", 10);
+//        m_HipsRb.mass = m_ResetParams.GetWithDefault("hip_mass", 12);
         m_HipsRb.mass = m_ResetParams.GetWithDefault("hip_mass", 15);
     }
 

config/trainer_config.yaml

     time_horizon: 1000
     batch_size: 2048
     buffer_size: 20480
-    max_steps: 2e7
+    max_steps: 3e7
     summary_freq: 30000
     num_layers: 3
     hidden_units: 512

Project/Assets/ML-Agents/Examples/Walker/TFModels/WalkerDynamic17MStepsLocalRot.nn.meta

+fileFormatVersion: 2
+guid: e1adbf3a9d04441259d6327d42fcce3d
+ScriptedImporter:
+  fileIDToRecycleName:
+    11400000: main obj
+    11400002: model data
+  externalObjects: {}
+  userData: 
+  assetBundleName: 
+  assetBundleVariant: 
+  script: {fileID: 11500000, guid: 19ed1486aa27d4903b34839f37b8f69f, type: 3}

Project/Assets/ML-Agents/Examples/Walker/Prefabs/WalkerWithTargetPB.prefab.meta

-fileFormatVersion: 2
-guid: d792ac94ffaf549ba93b3082ced7cdf7
-PrefabImporter:
-  externalObjects: {}
-  userData: 
-  assetBundleName: 
-  assetBundleVariant: