Accelerometer tap detection for z probe

[oliof]

Topic says it all. I'd like to see the option to use tap detection to use an accelerometer as z probe. Klipper has a currently unmerged PR to do this.

[dc42]

@oliof it's on the wish list but not a high priority. It needs a high sampling rate to give low latency. The LIS3DH should be OK for this if we switch to its 8-bit mode, which can sample at around 5kHz. Or we could stick with 1344Hz sampling and accept higher latency, and therefore reduced accuracy.