Fix race condition in NodeProvideOutOfProcTaskHost

[surayya-MS]

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

[Copilot]

Pull Request Overview

This PR improves thread safety in NodeProviderOutOfProcTaskHost by converting two dictionary fields from IDictionary<int, T> to ConcurrentDictionary<int, T>.

• Changed field type declarations for _nodeIdToPacketFactory and _nodeIdToPacketHandler to use ConcurrentDictionary
• Updated initialization from Dictionary to ConcurrentDictionary
• Replaced Remove() calls with TryRemove() to use the concurrent dictionary API

[rainersigwald]

I'm not sure I see how this solves the problem. Can you elaborate please?

[AR-May]

I'm not sure I see how this solves the problem. Can you elaborate please?

oh, that's a mystery here. This fix solves the race condition in the prototype branch - I can attest to that fact. But neither me nor @surayya-MS (please correct me if you figured it out since our last sync) figured yet why it solves it, more precisely, why it runs into a race condition in the first place.

We need to investigate this bug a bit more