[ADD] Slash Metrics

This adds metrics for point and bond slashes, labeled by reason/chain/coin/etc where possible. This should give us additional information for more detailed charts and alerts. We ran this on a node recovered from a snapshot and the labeled metrics come through fine (ex. https://dashboards.dev.ninerealms.com/#slash) - once this runs on a sync'd node over a longer duration we'll be able to create more useful charts and alerts.