[FIX] account: partial reconcile unreconcile with deleted credit/debit move

`debit_move_id` and `credit_move_id` of
`account.partial.reconcile` must be required.

Not having one of them set on this model
does not make sense, you cannot have a reconciliation
with a debit move but without a credit move, for instance.

Databases already having the trouble,
having partial reconciliations without
either a debit or a credit move,
had issues for the computation of the
`payment_move_line_ids` compute field,
which relied on the fact these fields
were supposed to be required. This revision
makes a retro-compatibility patch for these
databases already having the issue.

opw-677709