This commit expands the in-line docs around updaterEnabled package variable used to affect release checking.
Along with clarifying specific details discovered when talking with @williammartin, I'm also removing a useless local variable.
This commit is a bit of refactoring to bring the extension update checking logic up to par with what is done with `gh` including creation of state file per extension and listening to env vars for disabling version checking.
This work is not complete as it does not address necessary test changes.
