Expose an API that opens a quickpick allowing users to select a Python environment

[DonJayamanne]

VS Code exposes an API to select the workspace folder, I think exposing a similar API to select a Python would be useful.
Note: This API would display a quick pick and return the selected Environment (it does not change the currently active env).

I can see this being used at least in 3 places today in the Jupyter extension and other personal extensions I have (Python environment Manager, Jupyter Launcher, etc).
I'm assuming other extensions could also benefit from this.

Features that would be useful in the quick pick (API):

• Ability to create a new env
• Ability to filter environments displayed in the list
• Ability to mark an item as suggested
• Ability to mark an item as currently selected.

[karrtikr]

Sounds like a useful API, marking as "needs proposal".

[DonJayamanne]

Please do not treat this as a partner ask, Jupyter extension does not need this, however it would be nice to have (the current API does allow us to build our own quick pick).
@brettcannon /cc