Port the U1 top cover purifier mode and the related start G-code
changes from Snapmaker's Orca (Snapmaker/OrcaSlicer#504 and
Snapmaker/OrcaSlicer#1005, as of 8931178229).
The start G-code sends SET_PURIFIER_MODE for strong cooling, weak
cooling or keep warm, picked from the lowest softening temperature of
the filaments used through min_vitrification_temperature, with
Snapmaker's thresholds and parameters. It also pre-extrudes the first
tool, and turns the part fan off for probing and back on for nozzle
cleaning.
U1 filament presets use Snapmaker's softening temperatures. U1 presets
that have no U1 version in Snapmaker's Orca use the value Snapmaker
gives that material on the U1.
* update snapmaker profiles. largely ported for Snapmaker Orca fork
* update prime volume
* set precise_outer_wall to 1
* Update per-material multi-tool ramming to the filament library
* Add per-filament overrides for toolchange retraction
* Set toolchange retraction per filament for Snapmaker U1
* set default support type to tree
* format snapmaker profiles