AzureDeveloperCredential: handling multiple tenant IDs

We need to publish documentation around working with the AzureDeveloperCredential, specially for multi-tenant cases.

Folks should have an easy way to understand what to expect when using the AzureDeveloperCredential from their applications; depending on the login they did for azd.

Some questions to be documented:
- I logged in azd using `azd auth login --tenant-id XX`. Should I expect getting tokens for tenant XX when running `azd auth token -o json` ? [XX might or might not be the user's home tenant]
- If my account has access to tenant A, B and C and I have one azd project for each tenant in different folders, does azd knows how to pick the right tenant when using the AzureDeveloperCredential?

This issue can be used to let folks to bring more questions and improve docs around a FAQ