sg start, use local universal-ctags by default, if available

Created by: jhchabran

We're using the dockerized version of universal-ctags because a long time ago, this was annoying to build on our machines. Nowadays, it's a package install away, on both ubuntu and mac.

Teammates working on the symbols service can still override the CTAGS_COMMAND to use a specific version of their choosing.

This should dramatically reduce the initial startup time, because we won't be building the dockerized version of universal-ctags when running the symbols service if it's already installed.

Universal ctags has been also added to sg setup on both mac and ubuntu.

Side note: some stuff with the oss commands was broken, fixed it along the way.

Test plan

Tested on my local machine, checked that the universal ctags is installable on ubuntu as well.

As for the pitfall of mistaking other ctags for the one we need, we check for +interactive in the help section of the command. I tested it in an ubuntu VM, installing universal-ctags after emacs will select the correct one, making the setup task working.