As the translog evolves towards a full operations log as part of the
sequence numbers push, there is a need for the translog to be able to
represent operations for which a sequence number was assigned, but the
operation did not mutate the index. Examples of how this can arise are
operations that fail after the sequence number is assigned, and gaps in
this history that arise when an operation is assigned a sequence number
but the operation never completed (e.g., a node crash). It is important
that these operations appear in the history so that they can be
replicated and replayed during recovery as otherwise the history will be
incomplete and local checkpoints will not be able to advance. This
commit introduces a no-op to the translog to set the stage for these
efforts.
Relates #22291
7946396fe6