This is a new type of CDC generation identifiers. Compared to old IDs,
additionally to the timestamp it contains an UUID.
These new identifiers will allow a safer and more efficient algorithm of
introducing new generations into a cluster (introduced in a later commit).
For now, nodes keep using the old identifier format when creating new
generations and whenever they learn about a new CDC generation from gossip
they assume that it also is stored in the v1 format. But they do know how
to (de)serialize the second format and how to persist new identifiers in
local tables.
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