Add metrics for Raft Snapshots. Attempt/success/fail (#1953)

Adding metrics for Raft Snapshot download. See
neo-technology/neo4j#28148

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Co-authored-by: NataliaIvakina <[email protected]>

Author: RagnarW

modules/ROOT/pages/monitoring/metrics/reference.adoc

@@ -579,6 +579,9 @@ The deprecated Raft core metrics are replaced accordingly by the Raft metrics in
 |<prefix>.cluster.raft.replication_maybe|Raft Replication maybe count. (counter)
 |<prefix>.cluster.raft.replication_success|The total number of Raft replication requests that have succeeded. (counter)
 |<prefix>.cluster.raft.last_leader_message|The time elapsed since the last message from a leader in milliseconds. Should reset periodically. (gauge)
+|<prefix>.cluster.raft.snapshot_attempt|Total number of attempts to download Raft snapshots triggered. (counter)
+|<prefix>.cluster.raft.snapshot_success|Total number of successfully downloaded Raft snapshots. (counter)
+|<prefix>.cluster.raft.snapshot_fail|Total number of failed Raft snapshot download attempts. (counter)
 |===