Add filament change from CLI

[gyscos]

Is your feature request related to a problem? Please describe. I would like to slice and generate gcode from a model file using the command-line interface.

Describe the solution you'd like Some CLI option to bring the same features as the GUI:

• specify a height in millimeters where a color change should happen
• optionally specify the new color to use

Describe alternatives you've considered Using custom after-layer gcode, with a condition on the layer height. Has to be careful to properly account for retraction. Also this workaround does not emit the "estimated time to next user interaction" gcode messages.

Additional context

• The current --colorprint-heights appears deprecated and does not seem to be doing much.
• Is it expected that these color changes are not exported as part of the print config?