Collect memory dumps for hung tests

[RussKie]

Resolves #3298

Proposed changes

• Spin up a background thread that signals at 15 minute mark, and looks for a dotnet.exe process that runs our tests.
• If one is or more processes are found, collect their heap dumps and kill those processes.

Microsoft Reviewers: Open in CodeFlow

[RussKie]

/cc: @weltkante

[davidfowl]

Hmm you shouldn't need this if you switch to vstest. We should sync on that

[weltkante]

when you do, keep in mind that WinForms requires some tests to be run in separate processes, hang diagnostics should cover those as well

[davidfowl]

If you control process launch then you need to replicate what the test host does. It's easier here since it's a single OS

[RussKie]

We should sync on that

Certainly, would love that.

I've found that the Arcade is now vstest enabled (dotnet/arcade#5347) but I couldn't see any clear guidance on what needs changing in the consuming repos.

[weltkante]

Considering that xunit.stafact nuget dependency is xunit-specific you'd need an equivalent for vstest (or build the infrastructure yourself for supporting multiple UI threads in vstest)

[RussKie]

I'm hoping there's a better proposal than to rewrite 50K tests from xunit to vstest...