Stock packaging calculator packaging type

This is a small technical bridge module that connects two existing features: the packaging quantity calculator and packaging types. It does not add new menus or screens; it changes how quantities are displayed wherever the packaging calculator is already used.

What changes for users: - When Odoo shows a quantity together with a packaging, it now uses the packaging type's code (or another chosen field of the packaging type) instead of the packaging's own name. - The display can be compact, meaning the quantity and the type label are shown together without a space, or with a space if compact mode is turned off. - The field used for the label and the compact setting are controlled by context values, so other modules or views can decide which packaging type field to show.

If a packaging has no packaging type, the module falls back to the standard behaviour and shows the packaging name as before.

The module touches the product model (product.product) and the abstract mixin product.qty_by_packaging.mixin, which is responsible for computing the quantity-by-packaging display. It also declares that the display computation depends on the language and on the packaging type display settings, so the shown text refreshes correctly when those change.

Because it installs automatically when both related modules are present, users do not need to enable it manually.