MSAL Python 1.21.0

[rayluo]

The API in this new version remains the same as the previous version.

Enhancements:

• Support getting an ssh certificate via broker (Use broker for SSH Cert feature #515)
• Support B2C's usage pattern of using client id as a scope (Cannot put client id into scopes, therefore cannot get access_token for Azure B2C #505, Allow using client_id as scope. Needed by B2C. #530)
• MSAL's token cache helper can now be used to store tokens returned by App Service's Managed Identity (Fallback to expires_on when expires_in is absent #519)
• Switch to a new set of regional endpoints (Switch to new region endpoints #513)
• Test matrix covers Python 3.11 (Test matrix covers Python 3.11 #512)

@xiangyan99, please follow up with the smoke tests.