[REF] stock_landed_costs: usability changes

- update label for account_journal_id
- remove cost lines explanation
- label of the LC name
- remove former cost per unit
- auto compute cost line when validating
- rename former cost into original value
- remove additional landed cost form the tree view
- stock_landed_costs: rename cost line into additional costs
- add a final value field (Lucky day: the field I had to add was already
  defined but not used.)
- use monetary field
- make weight and volume optional
- journal entry visible only if posted
- landed costs wording in settings
- raise of no transfers are defined before validating

task-59011