[FIX] stock: Add readonly constraint on product template in models stock quant/move

Avoid unwanted update of product_tmpl_id on product.product

Somehow, the field product_tmpl_id on product.product could be updated
to an unrelated product template, if the context key `default_product_tmpl_id`
is set when an inventory move is created through an update of
stock.quant.inventory_quantity.

Setting readonly to True on both stock.quant and stock.move product_tmpl_id
field prevents this unwanted update.

closes odoo/odoo#104602

Signed-off-by: William Henrotin (whe) <whe@odoo.com>