src: get rid of ClearWrap()

[bnoordhuis]

Continuing from #18656.

Commit 6bdc18c removes an erroneous ClearWrap() call that I think is indicative of a bigger problem.

Some persistent objects are sometimes destroyed by the garbage collector, sometimes by explicit action (e.g. closing of a handle), and that can leave the object in an inconsistent state.

My hunch is that most ClearWrap() calls can simply be removed.

[jrasanen]

@bnoordhuis So most ClearWrap functions should be removed? Which places do you think it could be left to exist?