Shard-level latencies generate a lot of metrics. This patch reduces the
the number of latencies reported by Alternator while keeping the same
functionality.
On the shard level, summaries will be reported instead of histograms.
On the instance level, an aggregated histogram will be reported.
Summaries, histograms, and counters are marked with skip_when_empty.
Fixes#12230Closesscylladb/scylladb#17581