Set 'startHidden' flag on tor process in tor-launcher

We have to maintain two different builds of tor.exe on windows, one with the -mwindows compile time flag and one without. This flag prevents a cmd.exe window from opening when the tor.exe process is started by tor-launcher.

In tor-launcher, we could just set the 'startHidden' flag ( https://searchfox.org/mozilla-central/source/xpcom/threads/nsIProcess.idl#82 ) on the tor nsIProcess ( https://gitlab.torproject.org/tpo/applications/tor-launcher/-/blob/master/src/components/tl-process.js#L533 ) and then we can most likely get rid of the -mwindows flag on the tor build.

With the cmd.exe issue fixed in tor-browser/tor-launcher, we will not need to maintain multiple different builds of tor.exe on windows.