Configurable Timer needed to close idle circuits

[mikegorman-nf]

Circuits are marked idle after 60s but there is no system to close them. "Abandoned" circuits can be idle indefinitely, logging warnings and taking some small amount of resources per circuit. Having a timer available to close those would be nice to keep the environment cleaner. Having it configurable with a long default (24H?) should protect long-running connections and allow for specific use case configuration.

[plorenz]

Plan is to address this with a per-service configuration value, defined on the service entity. The default value of 0 will mean no maximum timeout.