Allow to directly connect to PWSH in Azure Cloudshell bypassing bash

[artisticcheese]

Description of the new feature/enhancement

Currently to launch powershell cloudshell in Windows Terminal one have to launch bash and then within bash you have to launch powershell ending up with shell running inside another shell plus additional time to perform those task on each run.

Proposed technical implementation details (optional)

Do the same what Azure portal offers where you are given a choice which shell you want when you connect to cloudhsell either bash or powershell and go directly into it.

[Don-Vito]

I wrote a short PoC where I read the preferred shell from API but instead of opening it immediately, I allow to choose a shell, where empty selection (pressing Enter) continues with a preferred shell. See below.

However, I believe the major issue here is with UX, because this change introduces additional user input. I guess we could somehow prevent this input from appearing every time, by caching it, but this might complicate things as well (Do we cache it as a part of login session? Separately? Might it create inconsistencies).

@DHowett, @cinnamon-msft - WDYT?

Default Shell

Custom Shell