Add per-shard metrics for strong consistency coordinator operations (latency, timeouts, bounces, status unknown) under the `"strong_consistency_coordinator"` category. These are analogous to the eventual consistency metrics in `storage_proxy_stats`, enabling direct performance comparison between the two consistency modes.
The metrics are simplified compared to `storage_proxy_stats` — no breakdown by table, tablet, scheduling group, or DC, only per-shard.
Fixes SCYLLADB-1343
Strong consistency is still in experimental phase, no need to backport.
Closesscylladb/scylladb#29318
* github.com:scylladb/scylladb:
test/strong_consistency: verify metrics
strong_consistency: wire up metrics to operations
strong_consistency: add stats struct and metrics registration
129f193116