Switched to ES modules for this commit.

Implemented a function for getting GETINFO net/listeners/socks.

Remove unused assets.

Remove part of the about:tor additions from the torbutton commit to
move them to a commit on their own.

Removed unused mobile CSS

Moved aboutTor.xhtml to its new location and make it use more modern IPC
mechanisms.

First step toward IPC modernizartion (WIP).

Populate the page with real data.

Do not send data to about:tor on Torbutton anymore.

Move the Tor checking functions from torbutton.js to its file.
Also, rework the file a little bit, to make it an ES module, and import
the file directly, instead of using XPCOM.

Get the TorCheckService by importing the module, instead of using XPCOM.

Continued to rework TorCheckService.

Use a ConsoleAPI logger instead of the old Torbutton logger.

Reworked the local check, to delegate TorProtocolService to get the
listeners, and then improved the rest of the function, in general.

Finally, changed the topic name, and notify observers whenever the
status change, also if suddenly the check succeeded.

If we know that TorCheckService already failed, or that we are invoked
by an observer, do not wait for the test again, but show the result
immediately.
If it changes, the observer will trigger another page update.

Reworked the remote check of TorCheckService.

Move the check service to the about:tor commit.

Move TorCheckService here, since it is used only for about:tor.
Move here also the check for the TOR_DEFAULT_HOMEPAGE variable.

Stop customizing the about dialog in the Torbutton commit.

Customize the about dialog in the branding commit.

This actually depends on the strings commit, but maybe we could move it
to earlier in the patchset.

Bug 41842: Remove the logic to remove cookies|protected-*json

Removed the function that deleted some cookie JSON preference file.
The function was introduced in
torbutton@2dfa0e0c in 2019.
However, since we have had a watershed release, we don't need it
anymore.
And because of the 12.0 watershed, we do not need to mess up with some
these preferences anymore.

Bug 41842: Stop migrating torrc: we have not written control/socks
ports to it for years!

Bug 41845: Do not force pref values for non-PBM users anymore.

A preference cleanup function will be added later, when we finish
removing all the torbutton stuff.

Add default values for preferencs in the logger.
I anticipated the removal of the old defaults, since the logger is going
away with another MR, but the cleanup function was already in this one.

Remove the defaults for the old preferences we are deleting.

Bug 41845: Clear user values for the prefs we decided not to force
anymore.

Also, remove some old Torbutton preferences.