Remove RoutingTableHandler and snapshotter, use database for route stats

- Remove RoutingTableHandler as PrefixHandler maintains live_routes table
- Update server to get route counts from database instead of in-memory routing table
- Add GetLiveRouteCounts method to database for IPv4/IPv6 route counts
- Use metrics tracker in PrefixHandler for route update rates
- Remove snapshotter entirely as database contains all information
- Update tests to work without routing table

internal/database/interface.go

@@ -41,6 +41,7 @@ type Store interface {
 	UpsertLiveRoute(route *LiveRoute) error
 	DeleteLiveRoute(prefix string, originASN int, peerIP string) error
 	GetPrefixDistribution() (ipv4 []PrefixDistribution, ipv6 []PrefixDistribution, err error)
+	GetLiveRouteCounts() (ipv4Count, ipv6Count int, err error)
 
 	// Lifecycle
 	Close() error