backend doesn't grab instance from service

[blakejohnson]

Describe the bug

It is possible for the instance attached to the service to not get passed to the backend object. Only occurs when a user has access to a backend via multiple instances.

Steps to reproduce

service = QiskitRuntimeService(channel="ibm_quantum", instance="hgp1")
backend = service.get_backend("ibm_algiers")
# ... returns a non-matching hgp
print(backend._instance)

Suggested solutions

I suspect that somewhere around here there are a few instances of instance that should be instance_filter.

Additional Information

• qiskit-ibm-runtime version: 0.16.1
• Python version: 3.11
• Operating system: macOS