Enhancement: add support to test single connected PSU on dual PSU switch

[claudebouchard-arista]

Some plaftorms , like the CCS-710P-16P use 2 Power supply, one being a POE IN power supply and the other one an AC PSU.
It is very likely that only one of them would be connected at at time ( they dont offer hitless failover if both are connected)

Is it possible to add an option to VerifyEnvironmentPower so a test would not fail of ONE of the 2 power supply is not prensent, but still making sure the other one is OK ( and not other status)

show system environment power | json
{
    "powerSupplies": {
        "1": {
            "modelName": "PWR-280-ADP",
            "capacity": 280.0,
            "dominant": true,
            "state": "ok",
            "uptime": 1776348902.8383687,
            "fans": {},
            "tempSensors": {},
            "managed": false
        },
        "2": {
            "modelName": "PWR-PD",
            "capacity": 0.0,
            "dominant": false,
            "state": "powerLoss",
            "fans": {},
            "tempSensors": {},
            "managed": false
        }
    }
}

[carl-baillargeon]

To the implementer, let's add a knob to the input:

min_count: PositiveInteger | None = None
"""Optional minimum number of power supplies required to match the accepted states and voltage. If not provided, all power supplies must match."""