The symbol check output the HTML message for each item. This is _very_
slow and can lock the system reponsiveness. Changing to a queue/flush
method is much faster
cherry-picked from 245b778454
The pin on grid test always used a fixed grid spacing of 25 mils. The
change uses the current grid setting for the on grid test. Grid sizes
below 25 mils are clamped to 25 mils to prevent issues when connecting
wires to pins in the schematic editor.
Fixes lp:1817896
https://bugs.launchpad.net/kicad/+bug/1817896