For historical reasons, WiredTiger writes a checkpointStart record to PALI for each checkpoint. In practice, however, that is no longer needed, and can be removed from the code.

We write checkpointStart records two places – at startup (i.e., to start the first checkpoint) and when finishing an existing checkpoint. See calls to __wt_disagg_begin_checkpoint() in conn_layered.c.

Assuming nothing breaks, we should also remove the logic from PALI that supports this call.

Assigning to the persistence team since it seems logically related to their existing work to support page compaction.