Product Query [3]: Polish the block presentation

[sunyatasattva]

As we are readying to make the Product Query block available to Feature Plugin users, here are a few tasks we should accomplish:

• Add a (Beta) label after the block name.
• Decide on a user-friendly block name. Current candidate is just: Products.
• Change the block icon.
• Add feedback block in the inspector with link to Airtable.
• (Maybe?) Add a notice in the block description mentioning the block is experimental and going through changes.
• Change the dev flag to a feature plugin flag.
• Add all currently available product elements as the default template.

cc @vivialice