In particular, allow grid positions to override line snapping if
they're a better match (and do this independently on x and y axes).
We already allow a nearer anchor to override, but that should be
based on a cartesian distance rather than independent axes.
Fixes https://gitlab.com/kicad/code/kicad/issues/6626
The snap range needs tuning to preference and monitor resolution. This
shifts the default range down for users until the customization bits are
implemented.
You can now enable and disable snap to grid when drawing/editing across
all apps. You can also tie snap to grid to the visibility of the grid
to allow rapid enable/disable via grid display.