[IMP] account: allow to reconcile taking amount from the label of the statement line

Task 2039772

Add a new amount matching mode by taking the amount from the label, based on a regex. The regex must contain a capture group. If multiple groups are matched, there will be an error.
Also add a 'remaining' option for the second line, that puts the remaining amount of the statement in the second line.

closes odoo/odoo#35143

Signed-off-by: Quentin De Paoli (qdp) <qdp@openerp.com>