ThreadLog captures and writes out non-mirror related logs

[handzlikchris]

We're seeing debug-error messages coming from our app code that have Mirror at the bottom of the stack-trace.

eg.

<correct stack trace begins here>
Mirror.ThreadLog:OnLateUpdate()
Mirror.NetworkLoop:NetworkLateUpdate()

The messages are also duplicated, we'll also get another one with correct stack trace.
eg.

Test Thread Log
UnityEngine.Debug:LogError (object)
UniTaskMirrorTest/<>c:<Test>b__0_0 () (at Assets/#Project/Scripts/UniTaskMirrorTest.cs:11)
System.Threading._ThreadPoolWaitCallback:PerformWaitCallback ()

And mirror will produce

[T3029] Test Thread Log
UnityEngine.Debug:LogError (object)
UniTaskMirrorTest/<>c:<Test>b__0_0 () (at Assets/#Project/Scripts/UniTaskMirrorTest.cs:11)
System.Threading._ThreadPoolWaitCallback:PerformWaitCallback ()

UnityEngine.Debug:LogError (object)
Mirror.ThreadLog:OnLateUpdate () (at Assets/Mirror/Core/Threading/ThreadLog.cs:97)
Mirror.NetworkLoop:NetworkLateUpdate () (at Assets/Mirror/Core/NetworkLoop.cs:206)

It seems to be down to how ThreadLog attaches itself as a log-handler for threaded messages in Mirror.ThreadLog.Initialize via
Application.logMessageReceivedThreaded += OnLog;

And then pumps the logs out in Mirror.ThreadLog.OnLateUpdate - which is why we're seeing them with Mirror stack-trace alongside out normal threaded logging.

Repro

1. Create app logger that attaches to Application.logMessageReceivedThreaded += HandleLog;
2. Add following behaviour

public class UniTaskMirrorTest : MonoBehaviour
{
    void Start()
    {
        Task.Run(() =>
        {                
            Debug.LogError("Test Thread Log");
        });
    }
}

3. Build and run
4. Mirror logger and custom-app logger will print error

Expected behavior
I'd expect Mirror ThreadLog to only log its own messages

Desktop (please complete the following information):

• OS: Windows
• Build target: Standalone
• Unity version: 2022.1.23
• Mirror branch: v83.2.1

[miwarnec]

@handzlikchris interesting.
feel free to disable it for now, it's only needed if you use ThreadedTransports.
we'll look into a fix in a bit