Discovered while analyzing payload of Russian Wikipedia (T340705#9682598)

Steps to replicate the issue (include links if applicable):

• In an incognito window visit any page on Russian WIkipedia

What happens?:
Both ext.cite.referencePreviews and ext.gadget.referenceTooltips are being loaded.

What should have happened instead?:
ext.cite.referencePreviews should not be loaded. This is an additional 24.9 KiB.

Other information (browser name/version, screenshots, etc.):
Since PopupsPlugin is responsible for loading the code we either need to make the module empty/smaller or update Popups to have a way to disable plugins under certain circumstances.

Some possible ideas:

• Can we use a skipFunction ?
• Can we make ext.cite.referencePreviews tiny and move the bulk of the code elsewhere?
• Can we define Attributes programatically?
• If none of the above, can we add logic to Popups to support this use case?