Improved frames for Anet A6 Y belt tensioner

Improved frames for https://www.thingiverse.com/thing:1959208 as the originals are just too weak

V3 uses M3 nuts, V4 must be tapped for an M3 screw

Includes a stand-off for the bearing hub so that the bearing is free to move, a nut trap for the bearing nut and counterbore so that a cap head screw can be used for the bearing