Fix update_transforms issues

[TokisanGames]

Fixes #584
Fixes #544

Issues addressed:

• Undo not reapplying manual offset when undoing (due to update_transforms being called on the undo)
• Update_transforms called on non-sculpting brushes
• Update_transforms affecting whole cell instead of only aabb
• update_transforms uses wrong/old height offset after swaping IDs
• Mesh assets not retaining height offset setting and other settings across restarts of the engine

Not done:

• Retaining manually painted height offset - possible future update

[TokisanGames]

#584 is collecting a lot of issues, so I'm limiting this PR to one at a time.

@Xtarsia Would you review this please?

[Xtarsia]

As per my comments, I think line 805 in data.cpp is the main culprit.

[Xtarsia]

the smaller AABB is actually usuable for much more constrained updates too, at line 833~ modify to:

				for (int i = 0; i < xforms.size(); i++) {
					Transform3D t = xforms[i];
					if (brush_rect.has_point(Point2(t.origin.x + global_local_offset.x, t.origin.z + global_local_offset.z))) {
						Vector3 height_offset = t.basis.get_column(1) * mesh_height_offset;
						t.origin -= height_offset;
						real_t height = _terrain->get_data()->get_height(t.origin + global_local_offset);
						// If the new height is a nan due to creating a hole, remove the instance
						if (std::isnan(height)) {
							continue;
						}
						t.origin.y = height;
						t.origin += height_offset;
						updated_xforms.push_back(t);
						updated_colors.push_back(colors[i]);
					} else {
						updated_xforms.push_back(t);
						updated_colors.push_back(colors[i]);
					}
				}

which prevents modifying the entire cell at once (tho the whole cell will still be itterated over)

[TokisanGames]

Those changes are in. So far this PR addresses:

• undo issues (due to update_transforms being called on the undo)
• update called only on sculpting brushes
• update only affecting aabb instead of whole cell

Outstanding:

• update_transforms uses wrong/old height offset after swaping IDs (bug)
• As for retaining height offsets, Terrain3DObjects stores the current height offset for each object. 🤔 (feature, won't hold up)

[Xtarsia]

As for retaining height offsets, Terrain3DObjects stores the current height offset for each object. 🤔

could increase the triple to a quadruple and store the (tool height) offset as a PackedFloat32Array perhaps.

and/or;

Very out of scope for this PR, I think an extra foliage transform tool might be a better way to go, a brush with expand/shrink (to modify scale of existing xforms) and raise / lower. A foliage color tool could be nice as well.

[TokisanGames]

@Xtarsia Thanks for your help. Improvement ideas added to #43

[TokisanGames]

Some how I dropped the limit update to brush size rather than whole cell. Fortunately I found it in my reflog. Added in 5ab6742