Bug 29483: Check ItemsAnyAvailableAndNotRestricted once per patron

Bug 29483: Check ItemsAnyAvailableAndNotRestricted once per patron

ItemsAnyAvailableAndNotRestricted can take a long time and create nested loops.
We can check it once per patron, however, this requires us to flip the loops.
Since an item can only be used once, we now add a check to see if this item has already
been assigned to a borrower.

To test:
1 - Find or create a biblio with 100 items
2 - Place ten 'Next available' holds on a biblio
3 - Set preference 'AllowRenewalIfOtherItemsAvailable' to 'Allow'
    Set circ rules 'On shelf holds allowed' to 'If any unavailable'
4 - Checkout one of the items to a patron, backdated to be overdue
5 - Note a long loading time for the patron's checkouts
6 - Apply patch, restart_all
7 - Patron loads much faster

Signed-off-by: Andrew Fuerste-Henry <andrew@bywatersolutions.com>
Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>
Signed-off-by: Fridolin Somers <fridolin.somers@biblibre.com>