ERMs created in `calculate_vnode_effective_replication_map` have RF computed based
on the old token metadata during a topology change. The reading replicas, however,
are computed based on the new token metadata (`target_token_metadata`) when
`read_new` is true. That can create a mismatch for EverywhereStrategy during some
topology changes - RF can be equal to the number of reading replicas +-1. During
bootstrap, this can cause the
`everywhere_replication_strategy::sanity_check_read_replicas` check to fail in
debug mode.
We fix the check in this commit by allowing one more reading replica when
`read_new` is true.
Fixes https://scylladb.atlassian.net/browse/SCYLLADB-1147Closesscylladb/scylladb#29150
503a6e2d7e