The direct failure detector operates on abstract `endpoint_id`s for
pinging. The `pigner` interface is responsible for translating these IDs
to 'real' addresses.
Earlier we used two types of addresses: IP addresses in 'production'
code (`gms::gossiper::direct_fd_pinger`) and `raft::server_id`s in test
code (in `randomized_nemesis_test`). For each of these use cases we
would maintain mappings between `endpoint_id`s and the address type.
In recent commits we switched the 'production' code to also operate on
Raft server IDs, which are UUIDs underneath.
In this commit we switch `endpoint_id`s from `unsigned` type to
`utils::UUID`. Because each use case operates in Raft server IDs, we can
perform a simple translation: `raft_id.uuid()` to get an `endpoint_id`
from a Raft ID, `raft::server_id{ep_id}` to obtain a Raft ID from
an `endpoint_id`. We no longer have to maintain complex sharded data
structures to store the mappings.
e086521c1a