Make KeyMatrix row output switch faster

[dhalbert]

KeyMatrix was giving false readings with the NeoKey Ortho matrix, with the first column's key in most rows.

This was extremely confusing for a while, because it seemed to be related to pulls not being set properly. But the problem was really that when the row is changed from an output back to an input, it took a little too long to switch levels, due to the relatively weak internal pull resistor. Adding a delay of even 1us fixed the problem. But the best fix is to flip the output value back to what the pull will be, before switching back to being an input. That allows the output to change quickly due to being actively driven instead of just being changed through a pull.

Another confusion was that the original code worked fine when columns_to_anodes was True. But for the NeoKey Ortho, it needs to be False, and the time it takes to switch levels was perhaps a wee bit longer.

@jepler you may wish to test this too if you are trying out the NeoKey.

[kattni]

Tested successfully with the NeoKey Ortho Snap-Apart full sheet. Thanks for the fix!