Added cancellation token to device credentials request

[msmolka]

Changes

Please describe both what is changing and why this is important. Include:

• Endpoints changed
  • get device credentials
• Classes and methods changed
• DeviceCredentialsClient.GetAllAsync
• A summary of usage if this is a new feature or change to a public API (this should also be added to relevant documentation once released)
  • allow cancel request of get device credentials endpoint. Added support for cancellation token.

Testing

Please describe how this can be tested by reviewers. Be specific about anything not tested and reasons why. If this library has unit and/or integration testing, tests should be added for new functionality and existing tests should complete without errors.

• This change adds unit test coverage

• This change adds integration test coverage

• This change has been tested on the latest version of the platform/language or why not

Checklist

• I have read the Auth0 general contribution guidelines

• I have read the Auth0 Code of Conduct

• All existing and new tests complete without errors

[frederikprijck]

Thanks!