Ensure we block on autoselection when no interpreter is explictly set by user

[karrtikr]

Will add tests once @kimadeline confirms this fixes the issue.

[kimadeline]

It works! 🥳

I am hitting a second problem, although that might be by design:

1. The first time updateDisplay is called the interpreter is python, so it will trigger auto-selection, so far so good;
2. The auto-selection logic will query interpreterService.getInterpreters, and it will return only the cached interpreters, so the interpreter that will be displayed in the status bar is going to be one of my global interpreters;
3. Then the auto-selection will be triggered again, this time by ExtensionActivationManager.activate, and this time the local virtual environment selected will be returned, but there is no updateDisplay call to reflect that change.

I assume 2. is by design, so do we want to do anything about it? I will file a separate issue: #16727

[karthiknadig]

@kimadeline @karrtikr I think 2 is a problem but in the discovery code. For globals it should return cached. For locals it should return cached local environments, if there are none cached then it should looks for one and return anything it finds.

[karrtikr]

@karthiknadig For now to keep things simple we decided to ignore cache for both global and local envs the first time. If we have performance issues we can optimize it later.