Add bearerFormat hint to auth decorators

### Clear and concise description of the problem

https://spec.openapis.org/oas/v3.1.0.html#fixed-fields-22

It should be easier to add the bearerAuth hint to the generated openapi spec for auth. For example, it is not currently possible to generate:
```yaml
securitySchemes:
bearerAuth:
type: http
scheme: bearer
bearerFormat: JWT
```
which you can see in the examples in the linked openapi spec.
This feels common enough that it should be possible esp. given it is possible in the raw openapi spec

### Checklist

- [x] Follow our [Code of Conduct](https://github.com/microsoft/typespec/blob/main/CODE_OF_CONDUCT.md)
- [x] Read the [docs](https://typespec.io/docs/).
- [x] Check that there isn't already an issue that request the same feature to avoid creating a duplicate.