[onboarding experience improvement] Region capacity check

[savannahostrowski]

After region is selected check if:

availability - region is too busy to create cosmo db account

[ellismg]

I really hope we can leverage ARM primitives here - the problem of "will this deployment succeed or hit capacity issues" is not a problem specific to azd - anyone using ARM Deployments can hit this same issue and so I hope we can minimize the amount of azd specific work we do here.

Depending on how we solve this - it may have deep implications on Pulumi and Terraform support.

[puicchan]

This issue surfaced again for the unmoderated getting started with azd study conducted in Q4 2022. 2 out of 8 customers encountered this issue. Quote from user study: "I chose the wrong.. I am having issues with the region. It doesn't give me a lot of detail."

[puicchan]

Also, the error message for one of the customers - pretty "messy"

[savannahostrowski]

Related to #468

[savannahostrowski]

I'm going to close this in favour of #468 since there's considerable overlap.

[savannahostrowski]

Important for: Azure-Samples/azure-search-openai-demo#252