testfx: [3.0 regression] Unable to run a test with timeout in STA ApartmentState

Describe the bug

MSTest v2 ran all tests in STA ApartmentState when executed in a .NET Framework runtime. v3 runs “normal” tests still in STA, but tests that have a TimeoutAttribute applied now run in MTA.

Steps To Reproduce

Run these tests with various versions of MSTest and runtimes:

[TestMethod]
public void TestMethod1()
{
    // Outputs:
    // MSTest   net7.0   net48
    // 2.2.10   MTA      STA
    // 3.0.2    MTA      STA
    Console.WriteLine(Thread.CurrentThread.GetApartmentState());
}

[TestMethod, Timeout(1000)]
public void TestMethod2()
{
    // Outputs:
    // MSTest   net7.0   net48
    // 2.2.10   MTA      STA
    // 3.0.2    MTA      MTA    <-- Problem
    Console.WriteLine(Thread.CurrentThread.GetApartmentState());
}

Expected behavior

Either MSTest v2 behavior should be retained, or I should have a way to force STA on an unit test.

Actual behavior

Tests with timeout always run in MTA.

Additional context

I need STA to run UI (WPF) tests. Those tests try to execute WPF commands which now fail with InvalidOperationException: The calling thread must be STA, because many UI components require this.

This is most likely a side effect of #1296 The package “MSTest.STAExtensions” which is mentioned in #21 does not help/work, see saikrishnav/testfxSTAext#5 Related: #320

AB#1822144