Layered cursors do not currently support explicit use of the checkpoint=... configuration option.  Mongod doesn't use it with disagg, and has no plans to use it.  However, test programs use it: test/checkpoint does verification of what's in (and not in) the last checkpoint checkpoint=WiredTigerCheckpoint, and a moderate number of python tests use it as well.

This ticket proposes adding support for opening the last checkpoint (only) via checkpoint=WiredTigerCheckpoint , but not adding support for named checkpoints or opening other checkpoints.  Layered cursors on a follower already open the stable cursor on the last checkpoint, so it would be rather easy to support on either leader or follower - using the same code to open the last checkpoint, and not open an ingest table, and disallow write operations.

The benefit is 1) we don't have to redesign or change the flow of test/checkpoint, 2) Python tests that use the last checkpoint cursor can now run to completion, which may give broader coverage to other areas of the API.