Make toolbar icon changes compatible with service worker

Background / User story

Manifest v3 forces us to run our background scripts in a service worker, which can be suspended/terminated at any time. Therefore we have to make sure that we add all event listeners synchronously, or they may not be called when the service worker activates.

Potential breakage:

• Icon changes not applied (incl. when switching tabs during ongoing icon animation).

What to change

• Design: N/A
• Research: N/A
• Spec: N/A
• Legal: N/A
• Development: Adjust code to add all event listeners synchronously:
  • browser.*.addListener()
    • lib/browserAction: setBadge()/setIconImageData()/setIconPath()/toggleBadge()
      • tabs.onReplaced
        fallback for prerendered tabs

Hints for testers

See list of potential breakage under "Background".

Hints for translators

N/A

Further information

See also ui#1070 for information on which code is run on service worker activation.