Bug 29869: Make ModReserveFill a (temporary) wrapper for Koha::Hold->fill

Bug 29869: Make ModReserveFill a (temporary) wrapper for Koha::Hold->fill

Before diving into removing ModReserveFill, I propose this:

In order to perform real-life testing of the new Koha::Hold->fill
method, this patch makes the ModReserveFill method, just call the new
one.

To test:
1. Apply this patchset
2. Run:
   $ kshell
  k$ prove t/db_dependent/Koha/Hold* \
           t/db_dependent/Hold* \
           t/db_dependent/api/v1/holds.t \
           t/db_dependent/Reserves* \
           t/db_dependent/Circulation* \
           t/db_dependent/SIP/*
=> SUCCESS: Tests pass!
3. Sign off :-D

Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>
Signed-off-by: Kyle M Hall <kyle@bywatersolutions.com>
Signed-off-by: Fridolin Somers <fridolin.somers@biblibre.com>