WT-11007 introduced some diagnostic information to track split history within pages. This was an attempt to improve the debuggability of bugs involving split generations, in particular, WT-10789. WT-10789 saw a segmentation fault when trying to access pindex on a page likely due to the page being free’d from another sessions stash. To improve this further we should add a similar history buffer to the session to track when we free the split-gen stash. By tracking this we could verify which thread freed the memory in WT-10789 and when. Here's an example of what that history would look like:
 

-exec p session->stash_hist[0]
$2 = {
  name = 0x7ffff79c7cbb "WT_SESSION.commit_transaction", 
  func = 0x7ffff79ccdd0 <__PRETTY_FUNCTION__.0> "__stash_discard", 
  gen = 5, 
  oldest = 6, 
  time_sec = 1686035499, 
  line = 370, 
  len = 9
}