Bug 30920: Add caching to GetAuthorizedValueDesc

Bug 30920: Add caching to GetAuthorizedValueDesc

This patch adds caching to C4::Biblio::GetAuthorisedValueDesc for performance.

We cache each hash involved in the method use for description lookup and
we're careful to clear said caches appropraitely on changes.

Signed-off-by: Nick Clemens <nick@bywatersolutions.com>
Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>
Signed-off-by: Tomas Cohen Arazi <tomascohen@theke.io>
(cherry picked from commit ab866f040dc72da28ed59f3bf16505bfba47ed21)
Signed-off-by: Matt Blenkinsop <matt.blenkinsop@ptfs-europe.com>