Add ContinuousAccessEvaluation

[RickWinter]

Add CAE support in C++.

### Tasks
- [ ] Modify BearerToken policy to handle CAE
- [ ] Add options for token requests
- [ ] Update credentials to do the right thing with options
- [ ] Add protocol for token requests
- [ ] Seperate token caches to not cache CAE with non-CAE

### Tasks
- [ ] Add Client to test feature, ARM?

[ahsonkhan]

This feature is blocked on MSAL support for CAE in C++