Remove features from the unified search button

Spin off from #43503 (closed).

The new "unified search button" has some items that we likely should hide. Some of this should also be upstreamed.

• History. Technically "suggest Browsing history" is switched on for users. But we should probably hide this in permanent private browsing. Upstream this.
• Actions. A selection of quick actions.
  • Open Firefox View. Upstream this if mozilla-central still maintains the firefox view disable preference.
  • View add-ons.
  • Manage extensions.
  • Clear recent history. Hide in private browsing window. Upstream this.
  • Manage passwords. Hide if password store is not enabled? Upstream this? Decided against this.
  • Tor Browser help. This is actually a link to Firefox support. Replace with a "Tor Browser manual" option? Edit: replaced with a link to our support page instead. A new manual option can be added in #44070.
  • Refresh Tor Browser. Creates a new default profile for the user. This should work now, but this kind of thing is untested right now. Needs review.

/cc @donuts @felicia @pierov