[feature request] Battery recalibration from Nyx menu and include a screen saver

The batteries on our day 1 Switches are taking a toll, but it seems more like the stats of the battery are off rather than they're depleted. This I know because the battery started going haywire in OFW, jumping all over the place, so I decided to let it drain while being in HPL menu (I had reverted to OFW and didn't feel like prepping a SD card at this time) - the console was still alive the next morning despite being on 0% battery :)

Anyway, it would be nice if there was a battery tool in Nyx to reset the stats once the user has made a couple of proper charge recycles (I usually use a homebrew app for this, but the Switch was updated this week).

It would also be nice to have a simple screen saver so that when we put the Switch on drain, we don't burn in the screen.