* Restore `M-,' to allow continuing the last tags command. (Of course,
this doesn't have to be `tags-loop-continue', it could also be an
equivalent xref command, should one exist.)
There's no such command.
If you use `find-tag' often, you've probably rebound `M-.', and doing the same with `M-,' in your personal init file shouldn't be a problem.
* Bind `xref-pop-marker-stack' to another location, say, `C-x M-.',
alternatively make `C-u M-.' pop the state. (This is modeled after the
key binding used to pop the mark.)
That sounds much less convenient than the current binding.