In vstest mode the xunit test projects keep running, even after testhost is closed

Repro steps

This can be for example tested on https://github.com/microsoft/vs-streamjsonrpc, by forcing vstest mode in the test project:

<DisableTestingPlatformServerCapability>true</DisableTestingPlatformServerCapability>
<TestingPlatformDotnetTestSupport>false</TestingPlatformDotnetTestSupport>
<UseMicrosoftTestingPlatformRunner>false</UseMicrosoftTestingPlatformRunner>

If a user triggers a run in test explorer and then stops it mid-run, the test runner does not finish running it immediately.
It keeps running until completion. This causes file locking issues to appear.

Expected

vstest and testhosts pass in the parentprocessid, so that the child process closes immediately as soon as the parent closes.
if xunit test process would similarly pass in the parent process id, it could also detect parent closing and close immediately.

Reproduce the issue in the vstest-mode configuration against the linked vs-streamjsonrpc example, then trace how the xunit test process is started after testhost receives the parent process ID. Verify that stopping the run causes the child process to exit promptly and releases its file locks, including when the parent process closes unexpectedly.