[8.0] Sale Order Line onchange methods differs in form/tree view

**Onchange methods on Sale Order Line differs in form and tree view**

The commit which introduces this bug: https://github.com/odoo/odoo/commit/86f785ae1b2741ab67384f3022b971ab638daeb8#diff-23bba7b359689cdd952fbe0961ff11eeL41

So the situation is that you get different behaviour if entering a SO line in editable list and in form view (which you get when there are too much columns to display).

There are multiple strange situations because of this bug but the quickest to notice is that changing product in editable tree would cause the system to throw a warning when there's not enough stock to fulfil sale order ("You plan to sell ... but you only have ... available") where changing a product in a form view will not cause this check.

Notice that this PR would only make the system behave the same way in tree and form view, but it does not suggest that it's a good way of handling those onchanges.

Cheers