Investigate implementing run in terminal as a proper test explorer profile

[vinistock]

We originally implemented run in terminal in a way that makes it kind of independent from the test explorer. However, this does not have to be the case and in fact we can provide an even more integrated experience if we make running tests in terminal a proper profile.

That would mean that running tests in the terminal still updates the explorer's UI and the user will have the option to run a test in the terminal in continuous mode (watch and run).

The test explorer supports implementing multiple run profiles, so we could just add another one for run in terminal that has a different run handler.