Add sb omnibox handler, use it for reopening tabs in a different container

[ErichDonGubler]

Satisfies #1991.

[ErichDonGubler]

I think this is basically ready for review, disclaiming that I'm not familiar with the vast majority of the Sidebery codebase. I haven't brought it out of draft yet, though, because the premise of this feature hasn't been validated by maintainership (see #1991).

[mbnuqw]

Thanks, nice feature! Things that I'd change:

• Create service omnibox.ts and move that code to it. Export one function setupListeners and call it in background.ts: omnibox.setupListeners().
• Use different keyword, something easily accessible from other, non-latin keyboard layouts. e.g. = (it seems that this symbol is available in all supported locales (de, fr, hu, pl, ru, zh, ja) without switching to en layout, although I could be wrong).
• Translate default suggestion

You can make it mergable and I'll complete it myself (prob also add switching between panels).