Expose OneAuth Authentication on Windows as an Alpha Feature.

In #3216 @chlowell added support for authentication used OneAuth (an internal library that is shared across Microsoft for doing authentication). Right now this feature is hidden behind a build flag.

We'd like a way to ship this authentication strategy as an alpha feature that folks can opt into, so we can get coverage on the bits and also the feature unlocks some SSO scenarios like "your windows account knows about Azure and so now `azd` does as well, automatically via OneAuth".

This work item tracks enabling this as an alpha feature.

I think there are two things we need to do:

- [ ] Ensure we build with the `oneauth` tag in CI. This may require some help from @danieljurek as we need to get an MinGW environment set up to build and link the `azd` in this mode.
- [ ] Add a flag like `auth.enableOneAuth` that can be used to opt into this feature as we do for our other alpha features.