Updated metrics page for Tor applications

Tor Browser has seen a few changes with the 12.0 release which affect the usefulness of the current https://metrics.torproject.org/webstats-tb.html page:

• Applications team now only publishes 1 Tor Browser version per OS|arch pair, rather then ~36 we had before because all locales are now packaged in a single binary. Therefore the Tor Browser downloads and updates by locale tab can be deprecated (as you can see, all the stats for individual locales have dropped to ~0 while other is approaching the sum of the previous curves).
• We would like to track downloads and update pings per desktop Tor Browser OS|arch|channel tuple.
  • The currently supported OS|arch pairs are (see https://www.torproject.org/download/languages/ ):
    • Linux|x86
    • Linux|x86_64
    • Windows|x86
    • Windows|x86_64
    • macOS|universal // aarch6 and x86_64 are bundled together for macOS
  • The currently supported channels are release and alpha
• (dupe of #29835 ) We would like to track downloads for our Android Tor Browser releases by aarch (aarch64,arm,x86, and x86_64) and channel (release and alpha) pair (see https://www.torproject.org/download/#android and https://www.torproject.org/download/alpha/) (ie aarch64|alpha or x86|release)
• (dupe of #26030 ) We can deprecate the Tor Messenger downloads and updates tab
• We would like to add a tab for downloads of our tor expert bundle downloads (see https://www.torproject.org/download/tor/ ). These can be organized into an OS|arch|channel tuples (ie macOS|universal|alpha or linux|x86|release).

/cc @hiro