stats: Reorder code in counters.go.
stats: Reorder code in counters.go.

It should read as follows now:

- counters - single label
- counters - single label (function)
- counters - multiple labels
- counters - multiple labels (function)

and then the same thing for gauges as well.

This commit did not change any functionality.

Signed-off-by: Michael Berlin <d0bd1c6a4289581537082d4e674f75efbec53916@google.com>

mahak/vitess,vitessio/vitess,tinyspeck/vitess,tinyspeck/vitess,davygeek/vitess,HubSpot/vitess,dcadevil/vitess,tinyspeck/vitess,tinyspeck/vitess,alainjobart/vitess,dcadevil/vitess,mahak/vitess,HubSpot/vitess,alainjobart/vitess,enisoc/vitess,HubSpot/vitess,tinyspeck/vitess,mahak/vitess,HubSpot/vitess,HubSpot/vitess,davygeek/vitess,enisoc/vitess,tinyspeck/vitess,enisoc/vitess,mahak/vitess,davygeek/vitess,vitessio/vitess,alainjobart/vitess,alainjobart/vitess,davygeek/vitess,mahak/vitess,davygeek/vitess,dcadevil/vitess,dcadevil/vitess,mahak/vitess,vitessio/vitess,mahak/vitess,vitessio/vitess,HubSpot/vitess,enisoc/vitess,vitessio/vitess,tinyspeck/vitess,vitessio/vitess,alainjobart/vitess,dcadevil/vitess,mahak/vitess,dcadevil/vitess,enisoc/vitess,enisoc/vitess,HubSpot/vitess,alainjobart/vitess,dcadevil/vitess,alainjobart/vitess,HubSpot/vitess,vitessio/vitess,davygeek/vitess,vitessio/vitess,enisoc/vitess,alainjobart/vitess,davygeek/vitess