Rename stashes when they move around

Rename stashes when they move around

This is yet another patch in preparation for [perl #75176] (I keep
saying that.).

It uses the recently-added functions hv_name_add and hv_name_delete, to add and remove names when mro_package_moved is called.

mro_package_moved’s calling convention needed to change to make this
work, which is the bulk of the patch.

Code that was calling mro_package_moved was also doing it sometimes
when it was unnecessary. If the stash being assigned over had no name,
then there was no possibiiity of its being in the symbol table.

This probably fixes [perl #77358] (isa warnings), though I have not
tested that yet.

One user-visible change this introduces is that a detached glob whose
stash loses its name will no longer stringify the same way (a bit like
a glob that loses its stash pointer; except that it becomes
*__ANON__::foo instead of "").