Add election metrics

Author: RagnarW

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

@@ -481,6 +481,8 @@ label:deprecated[Deprecated in 5.15]
 |<prefix>.cluster.raft.snapshot_attempt|label:new[Introduced in 2025.01] Total number of attempts to download Raft snapshots triggered. (counter)
 |<prefix>.cluster.raft.snapshot_success|label:new[Introduced in 2025.01] Total number of successfully downloaded Raft snapshots. (counter)
 |<prefix>.cluster.raft.snapshot_fail|label:new[Introduced in 2025.01] Total number of failed Raft snapshot download attempts. (counter)
+|<prefix>.cluster.raft.pre_elections_triggered|label:new[Introduced in 2025.02] Total number of pre-elections triggered by this member. (counter)
+|<prefix>.cluster.raft.elections_triggered|label:new[Introduced in 2025.02] Total number of elections triggered by this member. (counter)
 |===