Allow retrieving all backend data

[jyu00]

What is the expected feature or enhancement?

Today on IQP website, one can download the data for all backends, even if they don't have access to actually run jobs on that backend. In qiskit-ibm-runtime, however, an exception is raised if I try to instantiate a backend (to get its data) that my instance doesn't have access to.

Acceptance criteria

One can instantiate a backend object even if their instance doesn't have access to it. An exception should only be raised if they try to run jobs on that.

[jyu00]

The backends() should include a new flag to indicate if people want just backends they can access (default), or all public backends.

[kt474]

After looking into this I don't think this currently possible. In order to instantiate a backend we need the backend configuration and users don't have access to /backend/{id}/configuration if they don't have access to the backend.

I thought we could use https://api.quantum.ibm.com/api/users/backends but this endpoint does not give the configuration