[2.0.x] Triple Z stepper / Z endstop

[TheLongAndOnly]

Adding support for a third z-stepper to support machines like SparkCube which have 3 spindles. Allows to add support for later automated z-bed leveling. In addition a third z-endstop including adjustment in-between the first and second/third axis is supported now.

Tested on SparkCube with RADDS and DUE including RADDS extension board V2.

[TheLongAndOnly]

Same here as other pull requests currently failing: error in void CardReader::removeJobRecoveryFile() "success" not defined.

[marcio-ao]

@TheLongAndOnly : Cool! This was on our wishlist :)

[TheLongAndOnly]

I have it running on my SparkCube on a RADDS/DUE combination (with RADDS extension board running Z2 & Z3). Seems to be working well. This also requires #11132 to work (plus an extension for Z3 micro stepping which is not yet in the pull requests).

Do we have a reasonable way to show dependencies between pull requests?

This PR works on its own. #11132 is required for the RADDS extension board, but only prepared for Z & Z2 so far. For the complete picture I need to issue an addition.

[TheLongAndOnly]

Hi, is there anything I can do go take this forward?

[thinkyhead]

Rebased, squashed, and split out example config changes to a separate commit.

[thinkyhead]

Rebased, applied adjustments, fixed bugs…

Also moved RADDS Extension Board V3 to a new PR at #11841.

Don't merge or push until after you do the following in Git Console:

git checkout triplez-2.0.x
git fetch origin
git reset --hard origin/triplez-2.0.x