Stores a cache of the convex hull similar to the bounding box. Modifies
the hull based on actions to allow complex footprint graphics without delay
Fixes https://gitlab.com/kicad/code/kicad/issues/7341
std::map is not move-constructable on MSVC because
it is not declared noexcept (and is not required to be
by the standard)
This means that a struct containing graphic_element
cannot be inserted into a vector with move semantics without
compile errors. However, wrapping it in a unique_ptr
works.