Bug 29121: Add new plugin exceptions

Bug 29121: Add new plugin exceptions

This patch introduces two new exceptions:

- Koha::Exceptions::Plugin::InstallDied
- Koha::Exceptions::Plugin::UpgradeDied

Tests are added for their stringification output.

To test:
1. Apply this patch
2. Run:
   $ kshell
  k$ prove t/Koha/Exceptions.t
=> SUCCESS: Tests pass!
3. Sign off :-D

Signed-off-by: Tomas Cohen Arazi <tomascohen@theke.io>
Signed-off-by: Kyle M Hall <kyle@bywatersolutions.com>
Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>