Catch FPEs on stm32, raise InternalError on same

[peterbarker]

No description provided.

[tridge]

nice! I think we need a test to run on stm32 boards (F4, F7, H7) to check the behavior. We need to make sure we keep flying after a FPE and get the right Inf etc

[peterbarker]

@tridge I used a patch on a bench-test Pixhawk which did a floating-point division-by-zero when switching into loiter. The Pixhawk continued to run.

I was considering adding an RC option to do it - but that's starting to feeling the "everything looks like a nail" part of ArduPilot.

I was wondering whether we should not clear these flags, just look at them. That would be a little safer but lose the ability to count the number of floating point exceptions occurring.

[peterbarker]

.... I should also point out that I'm not attempting to catch/handle the exception. These flags appear to be set regardless of any vectors, and clearing them shouldn't affect anything other than anybody else trying to monitor them.

[WickedShell]

Worth testing with some simple lua scripts that would provoke these. I could easily see them creating a FPE which we then would be panicing the user with, but since it's a script it isn't nearly as worrisome.

[peterbarker]

Stopped clearing the FPE registers as per devcall discussions.