No more unwanted infill, but fan kickstart

The 2.3.57 branch will be the next stable after some more bugfixes.

bugfixes

• Fix for fan speed-up time, should now work correctly
• Fix for fan kickstart, should now work
• Fix for auto dense infill:
  • better coverage
  • printed in the right order
  • has a 20% overlap with everything for a good grip (and not only perimeters as before)
• crash fix when layer_height is set at 0.
• better reliability for the clipper bug mitigation #1641

note: I haven't tested the linux & macos build.
You can have daily builds in the action menu of github.
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