Test crash in `TaskHostFactory_Tests.TaskNodesDieAfterBuild`

[rainersigwald]

This test failed in an unrelated PR build (#12667):

https://dev.azure.com/dnceng-public/public/_build/results?buildId=1180035&view=logs&j=6772b272-ab79-59eb-8cca-405ab5c4d2b5&t=77aa7d44-8ac6-58f9-07fa-1bd408749035&l=242

�[37m    Microsoft.Build.Engine.UnitTests.BackEnd.TaskHostFactory_Tests.TaskNodesDieAfterBuild(taskHostFactorySpecified: False, envVariableSpecified: True) [PASS]
�[m�[30;1m      Output:
�[m�[37m        [15:45:03.287] Attached to Sidecar (PID 8840)
�[mUnhandled exception. System.InvalidOperationException: Process was not started by this object, so requested information cannot be determined.
   at System.Diagnostics.Process.EnsureState(State state)
   at System.Diagnostics.Process.get_ExitCode()
   at Microsoft.Build.Engine.UnitTests.BackEnd.TaskHostFactory_Tests.ProcessTracker.<>c__DisplayClass1_1.<AttachToProcess>b__0(Object sender, EventArgs e) in /home/vsts/work/1/s/src/Build.UnitTests/BackEnd/TaskHostFactory_Tests.cs:line 366
   at System.Diagnostics.Process.RaiseOnExited()
   at System.Diagnostics.Process.CompletionCallback(Object waitHandleContext, Boolean wasSignaled)
   at System.Threading.ExecutionContext.RunInternal(ExecutionContext executionContext, ContextCallback callback, Object state)
--- End of stack trace from previous location ---
   at System.Threading.ExecutionContext.RunInternal(ExecutionContext executionContext, ContextCallback callback, Object state)
   at System.Threading.CompleteWaitThreadPoolWorkItem.System.Threading.IThreadPoolWorkItem.Execute()
   at System.Threading.ThreadPoolWorkQueue.Dispatch()
   at System.Threading.PortableThreadPool.WorkerThread.WorkerThreadStart()
   at System.Threading.Thread.StartCallback()
Aborted (core dumped)

Looks like this would be fixed in main by #12607. @YuliiaKovalova should we consider backporting to 18.0?

[YuliiaKovalova]

the real fix is here:
https://github.com/dotnet/msbuild/pull/12630/files#diff-3d94de5000051393eec6afc70d895d4ad492a8fc713e16477856f3d40531cddf

why it fails - the test expects to have running process within 3 secs , but sometimes process doesn't start !
Process was not started by this object, so requested information cannot be determined.

so in the PR above I added pulling