Bug 25159: Implement diffs in action logs for holds

Bug 25159: Implement diffs in action logs for holds

Test Plan:
1) Apply this patch
2) Run updatedatabase.pl
3) Restart all the things!
4) Enable HoldsLog
5) Perform various hold related actions
6) Observe the diff column is populated by a JSON string
   of the diff format generated by Struct::Diff

Signed-off-by: Kyle Hall <kyle@bywatersolutions.com>
Signed-off-by: Andrew Fuerste-Henry <andrewfh@dubcolib.org>
Signed-off-by: Emmi Takkinen <emmi.takkinen@koha-suomi.fi>
Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>
Signed-off-by: Katrin Fischer <katrin.fischer@bsz-bw.de>