`SetTestContext` should be done on the right `ExecutionContext` to correctly maintain async locals

[Youssef1313]

Describe the bug

Verify.MSTest generates the following:

  [global::System.CodeDom.Compiler.GeneratedCodeAttribute("Verify.MSTest.SourceGenerator", "1.0.0.0")]
  public global::Microsoft.VisualStudio.TestTools.UnitTesting.TestContext TestContext
  {
    get => global::VerifyMSTest.Verifier.CurrentTestContext.Value!.TestContext;
    set => global::VerifyMSTest.Verifier.CurrentTestContext.Value = new global::VerifyMSTest.TestExecutionContext(value, GetType());
  }

where CurrentTestContext is an async local that's expected to be read correctly when inside the test. This has regressed in 3.9.0.

We should propagate the execution context correctly when setting TestContext. After we have set TestContext, we should re-capture the execution context and use that in RunTestInitializeMethod

[Youssef1313]

FYI @SimonCropp

[SimonCropp]

@Youssef1313 thanks for looking into this

[sharadshahihw]

This looks like the issue we are going through in our unit tests. All the tests passed in 3.8.*, now some are failing in 3.9.0.
We are setting up fake HttpContext.Current in [TestInitialize] and using it on [TestMethod]. With 3.9.0 HttpContext.Current is null in the [TestMethod]

[Youssef1313]

@sharadshahihw The issue we know about here looks different from yours. The propagation of execution context between TestInitialize and TestMethod is supposed to be working correctly in 3.9.0. Can you please open a separate issue with a repro that shows the issue?

[sharadshahihw]

@Youssef1313
Created #5630