The trashcan mechanism could be streamlined

[markshannon]

The trashcan mechanism is over 20 years old and the code could do with a bit of streamlining.

There is a lot of indirection and a fair bit of redundancy as it implements its own depth counter.
Reworking the code to use the C recursion counter and removing most of the calls can streamline the code considerably.

Linked PRs

• GH-117760: Streamline the trashcan mechanism #117763