fix(atg): invalidate configurationValidationResult on ChargingStationEvents.updated...

fix(atg): invalidate configurationValidationResult on ChargingStationEvents.updated (#1977)

Subscribe to ChargingStationEvents.updated in AutomaticTransactionGenerator's
constructor so in-flight configuration mutations that reach any charging
station mutation emit cannot leave a stale memoized validation decision
behind. stop() still clears the cache as a redundant safety net.

deleteInstance unsubscribes the handler before removing the entry so the
retired instance is not retained via the charging station's listener array
across a getInstance/deleteInstance churn cycle.

Fixes #1965.