Use RLBox for sandboxing Graphite on macOS

In https://bugzilla.mozilla.org/show_bug.cgi?id=1610149 and child tickets Mozilla landed support for RLBox sandboxing Graphite on macOS as well. This ticket tracks the work for backporting the patches for Tor Browser.

To upload designs, you'll need to enable LFS and have an admin enable hashed storage. More information