Add a fix for the always_put_control_body_on_new_line lint

[bwilkerson]

It would be good to have a fix for the always_put_control_body_on_new_line lint.

It's possible that the fix would conflict with the formatter, in which case this might want to wait until we have a way to know whether the formatter is being used so that we can provide a fix that the formatter won't undo.

[bsutton]

Just a follow-up on this.
I have the formatter enabled and it does not appear to conflict with a possible fix for this lint.

If I have the code:

if (true) print('hi');

To fix it, I place a new line before the print

if (true) 
print('hi');

When I save the formatter then kicks in and replaces it with:

    if (true) {
      print('hi');
    }

My understanding is that the formatter isn't configurable, so I assume all users will see the same behaviour.

As such, if a fix for this lint generated the final form (above) then we have a working fix that doesn't conflict with the formatter.