1. Add a new style "Tree Slim". If enabled, tree
support branches are merged more aggressively, and the support volume
is minimized.
2. Enable support style, add back Snug for normal support.
3. Remove hybrid(auto) type and use "Tree Hybrid" style to represent it.
4. Fix a bug in plan_layer_heights that may generate empty layers when
layer height is set to 0.3mm.
5. Fix a bug where no raft is generated if there is no overhang.
6. Fix the bug where no bottom interface or bottom gap is generated when
tree slim is selected.
7. Use physical distance to calc radius
Change-Id: Iacd57018ae5496cdc9acd28551c44d1c88c53fe0
1. undef SUPPORT_TREE_DEBUG_TO_SVG
2. change default tree branch angle to 45 degrees
3. encourage tree neighbors merge faster
4. draw more loops at the top of trees for stronger support
Change-Id: I2edf6a2dddb3b6165c2519ee15e9a7ffaba9de94
(cherry picked from commit 3a9723b2e88a033b3298cd68daf9400265e984a1)
