Implement TokenRequestContext in azure_core

[heaths]

For #520, I'm going to pass in endpoint, credential, and scopes like this for now.

Originally posted by @cataggar in #61 (comment)

Eventually we'll need to follow what other languages have done to provide scopes consistently across clients.

[github-actions]

Hi @heaths, we deeply appreciate your input into this project. Regrettably, this issue has remained unresolved for over 2 years and inactive for 30 days, leading us to the decision to close it. We've implemented this policy to maintain the relevance of our issue queue and facilitate easier navigation for new contributors. If you still believe this topic requires attention, please feel free to create a new issue, referencing this one. Thank you for your understanding and ongoing support.