Threaded DRC access will write to this string, re-allocating the memory
without any synchronization between threads using the string. Comment
adding this listed performance as a reason for using shared strings.
Measured performance does not seem noticeably different in either case,
even with high-error count boards. If there is a case where the
performance is limiting, we can replace these wxStrings with
std::wstring and utilize fmt
Fixes https://gitlab.com/kicad/code/kicad/issues/9888
(cherry picked from commit 5327b10064)
The main issue was a parameter mismatch which caused On^2 behaviour
for zone layers.
But there are several other performance optimizations here, along
with status bar updating for zones while running the dissallow test.
Fixes https://gitlab.com/kicad/code/kicad/issues/8521
Jeff Young
Seth Hillbrand
Marek Roszko
Ian McInerney