Allow disabling Test Discovery Error popup

[brettcannon]

Discussed in #16861

^{Originally posted by superlevure August 4, 2021}
Hi,

Would it be possible to give the user the choice to disable the popup Test Discovery Error, please check the configuration settings [...] ?

It's really annoying to see it appear every time I open my workspace outside of the docker dev container, or in a project without tests

[karthiknadig]

This should be addressed in insiders. We show test discovery error as an error node in the Test explorer.