This series mark multiple high cardinality counters with skip_when_empty flag.
After this patch the following counters will not be reported if they were never used:
```
scylla_transport_cql_errors_total
scylla_storage_proxy_coordinator_reads_local_node
scylla_storage_proxy_coordinator_completed_reads_local_node
scylla_transport_cql_errors_total
```
Also marked, the CAS related CQL operations.
Fixes#12751Closesscylladb/scylladb#13558
* github.com:scylladb/scylladb:
service/storage_proxy.cc: mark counters with skip_when_empty
cql3/query_processor.cc: mark cas related metrics with skip_when_empty
transport/server.cc: mark metric counter with skip_when_empty