Change teardrop generation to rely more heavily on BOARD_CONNECTIVITY
for improved performance.
Add updating of teardrops on BOARD_COMMIT::Push().
Also converts m_CopperItemRTreeCache to std::shared_ptr.
We don't copy it around anyway, and having to create a new set
of std::unique_ptr's for each operation is likely to be more
expensive than std::shared_ptr's overhead.
Make "don't stroke" an explicit property in the GUI.
Silently enforce line width to >= 0 when stroking.
Make layouts between dialogs more consistent.
Interpret unspecified fill colour as layer colour.
Fixes https://gitlab.com/kicad/code/kicad/issues/11279