This is a hand-based squash+merge+clean of the Low Phase Drift
Calibration implemetned in HAL by Tom (based on branch
tom-v6-determinism-5.0.1). Tom's branch is based on release version
of wr-switch-sw that has been grately modified. Therefore, it
was not easy to just merge.

In principle, this commit includes Tom's code copy+pasted, as much
as was possible. In some places, I made "TODO-ML:" comments. These
places will be modified later with separate commits. This was
done to make the changes somehow clean and logical
- first Tom's code in this commit
- then further improvements in separate commits