Bug 37845: Remove C4::Members::DeleteExpiredOpacRegistrations

Bug 37845: Remove C4::Members::DeleteExpiredOpacRegistrations

This patch remove the subroutine C4::Members::DeleteExpiredOpacRegistrations.
The code is moved and adjusted to Koha::Patrons.
We now have 2 new methods:
  Koha::Patrons->filter_by_expired_opac_registrations
  Koha::Patrons->filter_by_safe_to_delete

Test plan:
Run the misc/cronjobs/cleanup_database.pl script with the
--del-exp-selfreg (as well as --verbose and --confirm) and confirm that
it behaves as expected

Note that it improve the output of the verbose mode and now tell if the something
is wrong with the config (syspref not set)

Signed-off-by: Sukhmandeep Benipal <sukhmandeep.benipal@inLibro.com>
Signed-off-by: Kyle M Hall <kyle@bywatersolutions.com>
Signed-off-by: Katrin Fischer <katrin.fischer@bsz-bw.de>