Bug 24080: Add 'payout' method to Koha::Account::Line

Bug 24080: Add 'payout' method to Koha::Account::Line

This enhancement adds a 'payout' method to Koha::Account::Line which can
be used to 'pay out' a credit to a patron.

When such a credit is 'paid out' this method will create a corresponding
account debit line with an amount equal to the amountoutstanding on the
original credit and the two acocuntlines will be immediately applied against
each other.

Test Plan:
1) Run the included tests and verify they pass.
2) Signoff

Signed-off-by: Kyle M Hall <kyle@bywatersolutions.com>
Signed-off-by: Tomas Cohen Arazi <tomascohen@theke.io>
Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>