Re-introduce "Blocks" view mode for Variants field

[boboldehampsink]

As was the default in Commerce < 5. Some clients really liked this because it was the fastest way to add variants.

Matrix still has it in Craft 5, so I'm hoping this is also possible for Variants.

[lukeholder]

Thanks for the feedback, due to the complexity of the variant edit screen I am not sure we will move back to this, but will keep it in mind and we discuss improvements in the future. Thanks.