Allow filtering of repeat `update` events on `ReconciliationSucceeded`

[murillodigital]

The generic webhook provider will send an event every time a ReconciliationSucceeded occurs, with a metadata.commit_status = update even when there are no changes between the current and previous reconciliation.

Please introduce some property (similar to Slack's provider https://github.com/fluxcd/notification-controller/blob/main/internal/notifier/slack.go#L83-L86 ) that will not send ReconciliationSucceeded events unless there has been some change in desired state.