Add ability to set `Session(..., max_time=...)` via `~/.qiskit/qiskit-ibm.json`

[samanthavbarron]

What is the expected feature or enhancement?

Add ability to set Session(..., max_time=...) via ~/.qiskit/qiskit-ibm.json. This would be very useful to be able to control this for all sessions that I create with a given service config.

Acceptance criteria

Adding the lines in qiskit-ibm.json similar to this

# cat ~/.qiskit/qiskit-ibm.json 
{
    "cloud": {
        "session": {
            "max_time": "4h"
        }
    }
}

would make it so that

service = QiskitRuntimeService(name="cloud")
backend = service.backend("...")
session = Session(backend)

is equivalent to

session = Session(backend, max_time="4h")