This ticket stems from
WT-10789, and relates to adding more split free functions with the purpose of improving the code coverage between btrees and their split free call functions.
When a page gets split, the old page will be split between two new in-memory pages. The old page will be called with __split_safe_free, which places the page into a stash where if no threads are accessing the variable, it will be scheduled to be freed.
The _split_safe_free makes sure that if there are no threads accessing the variable before freeing the object. Therefore it is quite lenient on where we can make this call _split_safe_free. The developer who takes this ticket will need to investigate all different places where we call the split free function. The idea is that we can uncover concurrent split free bugs more frequently.