[16.0][FIX] stock_available_mrp: variant BoMs

[danielduqma]

When a BoM is linked just to one variant through field product_id, it is taken in account when computing stock of the rest of variants of the same template.

AFAIK, there are two ways to link a BoM to a specific variant:

• Having one for the whole template, and linking attribute values to components with field bom_product_template_attribute_value_ids
• Linking a BoM to a variant with field product_id

The first one works right, but the second one can make a variant take in account a BoM that is linked to another variant of its template, so stock computations are not right.

[github-actions[bot]]

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