Launch directly the real tor also on macOS, rather than the shim script

On macOS, we don't launch tor, but we rename it to tor.real, and we invoke it through another script.

The script is pretty old, still contains Python stuff for obfs3 and we can do whatever it does in TorProcess.jsm.

So, I propose we keep decluttering tor-browser-build.git, and do the needed changes on tor-browser.git.