op-interop-mon: make RPCUpdater update interval configurable and wire via service

[MozirDmitriy]

• Add updateInterval field to RPCUpdater; use it in Run and processJobs.
• Extend NewUpdater to accept updateInterval; default to 1s when zero.
• Pass ms.PollInterval from InteropMonitorService.initUpdaters to NewUpdater.
• Update tests to use the new NewUpdater signature.
• Remove reliance on global updateInterval; no behavior change unless PollInterval is set.