Replaced torbutton's torbutton.svg with tor-browser's
torPreferencesIcon.svg to match new style

We also show a tooltip with the full domain on hover, so that it's not
necessary to copy it for users to see it.

Add strings for onion service error pages.

Replace "Keep Tor strong"
with    "Tor is free to use because of donations from people like you"

Add onionAuthViewKeys() and onionAuthRemove() Tor controller functions.

Add strings for "Remember this key" checkbox and the new
"Onion Services Authentication" preferences section.

Modify the Tor controller onionAuthAdd() function to remove support
for the nickname parameter (not supported by tor) and add some
missing parameter validation.

The link is now constructed in code (instead of coming from aboutTor.dtd)
and it is:
  https://community.torproject.org/LOCALE
where LOCALE is the current browser locale.

Since #24653 landed securityLevel strings are merged into torbutton.dtd.