Add adaptive card UI for Dev Box

Summary of the pull request

A Supplemental PR into Dev Home needs to be submitted first before checking this in: https://github.com/microsoft/devhome/pull/2639

This PR adds DevBox creation UI to the Azure extension and changes the following:

Adds the CreationAdaptiveCardSession which Dev Home will interaction when presenting the user with an initial creation page and a review page. The initial page contains a textbox, a projects combo box and a pools combo box. When Dev Home requests the creation session if the project and pools have not been retrieved yet, we retrieve them and get the Dev Boxes before returning the session.
Data for the pools for all projects is retrieved and sent in the adaptive card payload back to Dev Home.
Dev Home will use this data to dynamically update the data for the pools combo box based on the selection within the projects combo box.
I've added two adaptive card templates CreationForm.json and ReviewForm.json. The first will be sent as the initial page. When the user selects the next button in Dev Home the review page will be sent. If the user selects the previous button the creation page will be sent. If the user is on the review page and selects next we capture their input, stop the session and send it back to Dev Home. Dev Home will them re-show the review page back to the user once creation of the Dev Box has begun.

Video of flow: