[FR] Extend T command to allow raise or lower of both extruders at once.

[cdsmith69]

Is your feature request related to a problem? Please describe.

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Are you looking for hardware support?

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Describe the feature you want

I propose we extend the functionality of the T command to allow lifting or lowering both extruders at the same time.

We have already implemented lifting both extruders when doing G34 bed tramming, and to lower both and request the user clean both nozzles before autocalibration on the TAZ8. But this was done with gcode strings to set servo positions. Those gcode strings are hard coded and do not pick up the positions that were set in the tool head parameters in configuration.h. So now, if we want to edit the servo up and down positions, there are multiple places where edits will need to be made. If they are not all changed consistently, strange behavior could occur.

One solution would be fix those gcode strings that are setting servo angles to pick up the proper values from LULZBOT_SWITCHING_NOZZLE_SERVO_ANGLES. Then there would be only one place where the parameters need to be changed and the change would take effect wherever necessary. This is the whole point of having parameters defined in just one location in the config header files.

But I propose what I think is a better idea. We define new forms of the T command to command all tool heads to move to the up position or the down position. Perhaps "TU" for all up, and "TD" for all down. Then we could just use a TU or TD in the gocde strings anywhere we want to lift or lower both extruders. It will make the operation more generic and adaptable to future printers as well.

Additional context

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