feat: Add premium buttons to popup menu [EE 371]

Description

Feature branch for adding premium buttons to the popup menu.

Jira: https://eyeo.atlassian.net/browse/EE-371

Designs: https://www.figma.com/file/OKrwvb933QRjy2Ym2PTSoo/Wireframes-for-product-features?type=design&node-id=1053-2291&mode=design&t=CLnDLHm0wgCFw38a-0

To activate premium, in a webext console:

browser.runtime.sendMessage({type: "prefs.set", key: "premium_license_check_url", value: "https://qa-mock-licensing-server.glitch.me/"}).then(console.log); browser.runtime.sendMessage({type: "premium.activate", userId: "valid_user_id"}).then(console.log);

Source MRs:

1. !1060 (merged)
2. !1068 (merged)
3. !1083 (merged)