This series ensures that endpoint state changes (for each single endpoint) are applied to the gossiper endpoint_state_map as a whole and on all shards.
Any failure in the process will keep the existing endpoint state intact.
Note that verbs that modify the endpoint states of multiple endpoints may still succeed to modify some of them before hitting an error and those changes are committed to the endpoint_state_map, so we don't ensure atomicity when updating multiple endpoints' states.
Fixes scylladb/scylladb#14794
Fixes scylladb/scylladb#14799
Closes#15073
* github.com:scylladb/scylladb:
gossiper: move endpoint_state by value to apply it
gossiper: replicate: make exception safe
gms: pass endpoint_state_ptr to endpoint_state change subscribers
gossiper: modify endpoint state only via replicate
gossiper: keep and serve shared endpoint_state_ptr in map
gossiper: get_max_endpoint_state_version: get state by reference
api/failure_detector: get_all_endpoint_states: reduce allocations
cdc/generation: get_generation_id_for: get endpoint_state&
gossiper: add for_each_endpoint_state helpers
gossiper: add num_endpoints
gossiper: add my_endpoint_state
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