This commit removes `stock.scrap` model without affecting its
functionality from the user perspective.

Previous to this commit, when a user wants to scrap some product,
a record of `stock.scrap` is created which is a scrap order
containing info about the product, quantity, scrap reason, etc.
When a scrap order is confirmed, it generates a `stock.move` and
confirms it so that the quantity move is reflected in the quants.
That's why `stock.scrap` model itself provides no intrinsic value
and is dispensable.

This commit removes the model completely and relies only on
`stock.move.line` and `stock.move` to achieve the same functionality.
The menu item "Scrap" now redirects to a list of stock.move.lines that
has the new field `is_scrap` = true. If the user creates a new record
from the list, a draft `stock.move.line` is created initially. When it's
confirmed, it generates its `stock.move` and its state is changed to be
done.

The only fields that are added to `stock.move.line` to fully replace
`stock.scrap` are `scrap_reason_tag_ids` and
`should_replenish_scrapped`.

This commit also adds a new action to scrap a lot/serial number from its
form view directly.

Task-4606260