Bug 22456: Add Koha::Holds->filter_by_has_cancellation_requests

Bug 22456: Add Koha::Holds->filter_by_has_cancellation_requests

This patch adds that method. Which is covered by new tests.

To test:
1. Apply this patch
2. Run:
   $ kshell
  k$ prove t/db_dependent/Koha/Holds.t
=> SUCCESS: Tests pass!
3. Sign off :-D

Sponsored-by: Montgomery County Public Libraries
Signed-off-by: Tomas Cohen Arazi <tomascohen@theke.io>
Signed-off-by: David Nind <david@davidnind.com>
Signed-off-by: Kyle M Hall <kyle@bywatersolutions.com>
Signed-off-by: Tomas Cohen Arazi <tomascohen@theke.io>