Bug 33745: Lazily create attribute accessor methods in AUTOLOAD

Bug 33745: Lazily create attribute accessor methods in AUTOLOAD

Lazily create accessor methods when getting or setting an Koha::Object
attribute resulting in a significant speed up.

To test:
1) Run the benchmark.pl script
2) Apply the patch
3) Run the script again, Koha::Object accessors should be about 7 times faster
5) Ensure tests in t/db_dependent/Item.t still pass

Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>
Signed-off-by: Marcel de Rooy <m.de.rooy@rijksmuseum.nl>
Signed-off-by: Tomas Cohen Arazi <tomascohen@theke.io>