Add mechanism to delete a console tab

[dhruvisompura]

Add a trash can icon button to delete a console tab. This includes the session, and all associated console UI state for that session.

When a user clicks the trash can button for a console session tab:

1. Determine which session will be the new active session from the list of created sessions
2. Shutdown the session for the user if it hasn't already been done
3. Remove the session from all active session lists. We need to make sure the variables pane updates its list of sessions, and switches over to the new active session ONLY IF it was using the deleted session context.
4. Cleanup output channels? This may be out of scope.
5. Re-trigger diagnostics if the deleted console tab was the active tab

Testing

• Verify code diagnostics, code completion are re-triggered when active session is deleted. The new session context should be used
• Verify the console pane and interpreter dropdown updates its list of sessions shown to the user, and switches over to the new active session ONLY IF the deleted session was the foreground session.
• Verify the variables pane updates its list of sessions, and switches over to the new active session ONLY IF it was using the deleted session context
• Verify deleting a console tab triggers a graceful shutdown of the session and it is not hanging around by using the runtime debug pane