Context
After WT-16052 and WT-16053, we should have an extension example module and the ability to read/write to the turtle file. As such, we now implement the read KEK mechanism. During checkpoint-pickup and startup WT will need to do a PALI read to fetch the current active KEK. Furthermore we will pass the KEK to load_key().

Please follow the steps for "checkpoint pickup" and "startup" in the document.

Leader/Follower mode

• Startup (on existing WT): Verify that KEK blob is re-used
• Checkpoints using same KEK blob: KEK blob should be reused for each checkpoint

Follower Mode

• Verify checkpoint picks up correct KEK blob from metadata

Defintion of Done

• WiredTiger utilises load_key() within the checkpoint pickup or start up.
• Tests scenarios are created using either example and mock module