Previously, a reference point to calculate teardrop length was calculated
using a track segment. It can create significant position error with track arcs.
Now a arc is used to find this reference point.
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.
Also add a better handling of connected tracks when searching for a track connected
to a too short track to create a teardrop, search was stopped to Y connections.
Now the selected track is the longest of these 2 candidates.
Fixes#13006https://gitlab.com/kicad/code/kicad/issues/13006
Found via `codespell -q 3 -S *.po,./thirdparty,./Documentation/changelogs -L aactual,acount,aline,alocation,alog,anormal,anumber,aother,apoints,aparent,aray,ba,busses,dout,einstance,leaded,modul,ontext,ot,overide,serie,te,,tesselate,tesselator,tht`