[IMP] account: new setting to define a start for bank reconciliation

Payments older than the chosen date won't be proposed in the widget allowing to match payments with bank statements. This is useful if the db used invoicing for years and then installed accounting : users don't want to have to match all the old payments that were generated by invoicing with bank statements.

Was task 1829536
Was PR https://github.com/odoo/odoo/pull/24728