Add bearerFormat hint to auth decorators

[Kludgy4]

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:

  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

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[timotheeguerin]

It is actually possible to generate that today with @extension

playground

import "@typespec/http";
import "@typespec/openapi";

using OpenAPI;
using Http;

@extension("bearerFormat", "JWT")
model MyAuth is BearerAuth;

@service
@useAuth(MyAuth)
namespace DemoService {

}