bug#70784: Abolish string resizing

[Stefan Monnier]

>> Very nice.  For track-changes, the backtraces aren't as important,
>> because we often detect the problem only after the fact so the backtrace
>> may be unrelated (which is why I also record the recent keys).
> Right, recent keys are probably less important for `aset`.  I doubt the
> proposed warning would trigger very often but if it does, it should given
> ample information to the user.

Agreed.


        Stefan