- Remove the concept of "mcus". With only one target platform
(CircuitPython), it no longer makes a bunch of sense and has been kept
around for "what if" reasons, complicating our import chains and eating
up RAM for pointless subclasses. If you're a `board`, you derive from
`KeyboardConfig`. If you're a handwire, the user will derive from
`KeyboardConfig`. The end. As part of this, `kmk.hid` was refactored
heavily to emphasize that CircuitPython is our only supported HID stack,
with stubs for future HID implementations (`USB_HID` becomes
`AbstractHID`, probably only usable for testing purposes,
`CircuitPython_USB_HID` becomes `USBHID`, and `BLEHID` is added with an
immediate `NotImplementedError` on instantiation)
- `KeyboardConfig` can now take a HID type at runtime. The NRF52840
boards will happily run in either configuration once CircuitPython
support is in place, and a completely separate `mcu` subclass for each
mode made no sense. This also potentially allows runtime *swaps* of HID
driver down the line, but no code has been added to this effect. The
default, and only functional value, for this is `HIDModes.USB`
- Most consts have been moved to more logical homes - often, the main
or, often only, component that uses them. `DiodeOrientation` moved to
`kmk.matrix`, and anything HID-related moved to `kmk.hid`
This brings this naming into consistency with both fellow consts in the
same file (ex. LeaderMode is singular) as well as the variables in which
the consts are usually used (usually a `Firmware.unicode_mode` attribute
in a keymap).
