Make dictionaries concurrent in NodeProvideOutOfProcTaskHost (#12708)

Fixes #12660

### Context
The following assert fails:
`/mt /m` sometimes crashes with error:
```
Microsoft.Build.Framework.InternalErrorException: MSB0001: Internal MSBuild Error: Why are we trying to disconnect from a context that we already disconnected from?  Did we call DisconnectFromHost twice?
   at Microsoft.Build.Shared.ErrorUtilities.ThrowInternalError(String message, Exception innerException, Object[] args) in C:\Users\alinama\work\msbuild\src\Shared\ErrorUtilities.cs:line 69
   at Microsoft.Build.Shared.ErrorUtilities.VerifyThrow(Boolean condition, String unformattedMessage) in C:\Users\alinama\work\msbuild\src\Shared\ErrorUtilities.cs:line 195
   at Microsoft.Build.BackEnd.NodeProviderOutOfProcTaskHost.DisconnectFromHost(Int32 nodeId) in C:\Users\alinama\work\msbuild\src\Build\BackEnd\Components\Communications\NodeProviderOutOfProcTaskHost.cs:line 607
   at Microsoft.Build.BackEnd.TaskHostTask.Execute() in C:\Users\alinama\work\msbuild\src\Build\Instance\TaskFactories\TaskHostTask.cs:line 382
   at Microsoft.Build.BackEnd.TaskExecutionHost.Execute() in C:\Users\alinama\work\msbuild\src\Build\BackEnd\TaskExecutionHost\TaskExecutionHost.cs:line 636
```

### Changes Made
Changed `_nodeIdToPacketFactory` and `_nodeIdToPacketHandler` from
`Dictionary` to `ConcurrentDictionary`.

### Testing
Manually tested to make sure the error is not there.

### Notes

---------

Co-authored-by: Jan Provazník <[email protected]>

Author: surayya-MS

src/Build/BackEnd/Components/Communications/NodeProviderOutOfProcTaskHost.cs

@@ -86,13 +86,17 @@ internal class NodeProviderOutOfProcTaskHost : NodeProviderOutOfProcBase, INodeP
 
         /// <summary>
         /// A mapping of all of the INodePacketFactories wrapped by this provider.
+        /// Thread-safe to support parallel taskhost creation in /mt mode where multiple thread nodes
+        /// can simultaneously create their own taskhosts.
         /// </summary>
-        private IDictionary<int, INodePacketFactory> _nodeIdToPacketFactory;
+        private ConcurrentDictionary<int, INodePacketFactory> _nodeIdToPacketFactory;
 
         /// <summary>
         /// A mapping of all of the INodePacketHandlers wrapped by this provider.
+        /// Thread-safe to support parallel taskhost creation in /mt mode where multiple thread nodes
+        /// can simultaneously create their own taskhosts.
         /// </summary>
-        private IDictionary<int, INodePacketHandler> _nodeIdToPacketHandler;
+        private ConcurrentDictionary<int, INodePacketHandler> _nodeIdToPacketHandler;
 
         /// <summary>
         /// Keeps track of the set of nodes for which we have not yet received shutdown notification.
@@ -208,8 +212,8 @@ public void InitializeComponent(IBuildComponentHost host)
         {
             this.ComponentHost = host;
             _nodeContexts = new ConcurrentDictionary<int, NodeContext>();
-            _nodeIdToPacketFactory = new Dictionary<int, INodePacketFactory>();
-            _nodeIdToPacketHandler = new Dictionary<int, INodePacketHandler>();
+            _nodeIdToPacketFactory = new ConcurrentDictionary<int, INodePacketFactory>();
+            _nodeIdToPacketHandler = new ConcurrentDictionary<int, INodePacketHandler>();
             _activeNodes = new HashSet<int>();
 
             _noNodesActiveEvent = new ManualResetEvent(true);
@@ -602,10 +606,10 @@ internal bool AcquireAndSetUpHost(
         /// </summary>
         internal void DisconnectFromHost(int nodeId)
         {
-            ErrorUtilities.VerifyThrow(_nodeIdToPacketFactory.ContainsKey(nodeId) && _nodeIdToPacketHandler.ContainsKey(nodeId), "Why are we trying to disconnect from a context that we already disconnected from?  Did we call DisconnectFromHost twice?");
+            bool successRemoveFactory = _nodeIdToPacketFactory.TryRemove(nodeId, out _);
+            bool successRemoveHandler = _nodeIdToPacketHandler.TryRemove(nodeId, out _);
 
-            _nodeIdToPacketFactory.Remove(nodeId);
-            _nodeIdToPacketHandler.Remove(nodeId);
+            ErrorUtilities.VerifyThrow(successRemoveFactory && successRemoveHandler, "Why are we trying to disconnect from a context that we already disconnected from?  Did we call DisconnectFromHost twice?");
         }
 
         /// <summary>