Interpreter dropdown overhaul

[dhruvisompura]

The Interpreter dropdown is being simplified as a component to provide a better UX to users as part of the work for multiple sessions.

The dropdown is being replaced with a button that only has two jobs:

• show the name of the active sesison/env
• allow the user to switch between active sessions

The mechanisms for managing a session (start/stop/restart) are moving into the console pane.

When the button is clicked, a user should see a quick pick list to select an active interpreter session.