Bug 22454: Add Koha::Item::hidden_in_opac method

Bug 22454: Add Koha::Item::hidden_in_opac method

This patch adds a hidden_in_opac method that does the same calculation
done in GetHiddenItemnumbers, but for a single item, and doesn't get the
OpacHiddenItems syspref, but expects them to be passed as parameters (to
avoid multiple reads).

To test:
- Apply this patches
- Run:
  $ kshell
 k$ prove t/db_dependent/Koha/Item.t
=> SUCCESS: Tests pass!

Signed-off-by: Michal Denar <black23@gmail.com>
Signed-off-by: Josef Moravec <josef.moravec@gmail.com>
Signed-off-by: Nick Clemens <nick@bywatersolutions.com>