During the investigation of scylladb/scylladb#20282, it was discovered that
implementations of speculating read executors have undefined behavior
when called with an incorrect number of read replicas. This PR
introduces two levels of condition checking:
- Condition checking in speculating read executors for the number of replicas.
- Checking the consistency of the Effective Replication Map in
get_endpoints_for_reading(): the map is considered incorrect the number of
read replica nodes is higher than replication factor. The check is
applied only when built in non release mode.
Please note: This PR does not fix the issue found in scylladb/scylladb#20282;
it only adds condition checks to prevent undefined behavior in cases of
inconsistent inputs.
Refs scylladb/scylladb#20625
(cherry picked from commit c373edab2d)
68a55facdf