Promote orders with any `promotionable?` line-item

[ikraamg]

Description

Promote orders with any promotionable? line-item

The current behaviour seems incorrect, and also, there is a spec which is not clear about what the behaviour should be as the setup does not align with the test name.

Checklist:

• [x] I have followed Pull Request guidelines
• [x] I have added a detailed description into each commit message
• [ ] I have updated Guides and README accordingly to this change (if needed)
• [x] I have added tests to cover this change (if needed)
• [ ] I have attached screenshots to this PR for visual changes (if needed)

[mamhoff]

I think this is not correct behavior. The idea is here is that line items that should not be promoted will never be promoted, not even through an order-level promotion. An order-level promotion will promote all line items in the order, and if an order contains ANY non-promotionable items, it should not be promoted.