As much as we can, we should use core blocks when the functionality is mostly overlapping. In the case of the Post Title block, we don't need to add and maintain our own block most likely, so we should just brand the Post Title block instead.
This PR does the following:
* Creates a new block variation based on the core “Post Title” called “Product Title”.
* Brands it as our old “Product Title” atomic element.
* Use this variation as the default within the Product Query template.
* Also removes some old code used for variations before the namespace attribute was available on the core Query Loop and repurposes it to create this variation.
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