Continue to shuffle and burn stuff

- 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`

kmk/consts.py

@@ -3,49 +3,6 @@ try:
 except Exception:
     KMK_RELEASE = 'copied-from-git'
 
-CIRCUITPYTHON = 'CircuitPython'
-
-
-class HIDReportTypes:
-    KEYBOARD = 1
-    MOUSE = 2
-    CONSUMER = 3
-    SYSCONTROL = 4
-
-
-class HIDUsage:
-    KEYBOARD = 0x06
-    MOUSE = 0x02
-    CONSUMER = 0x01
-    SYSCONTROL = 0x80
-
-
-class HIDUsagePage:
-    CONSUMER = 0x0C
-    KEYBOARD = MOUSE = SYSCONTROL = 0x01
-
-
-# Currently only used by the CircuitPython HIDHelper because CircuitPython
-# actually enforces these limits with a ValueError. Unused on PyBoard because
-# we can happily send full reports there and it magically works.
-HID_REPORT_SIZES = {
-    HIDReportTypes.KEYBOARD: 8,
-    HIDReportTypes.MOUSE: 4,
-    HIDReportTypes.CONSUMER: 2,
-    HIDReportTypes.SYSCONTROL: 8,  # TODO find the correct value for this
-}
-
-
-class DiodeOrientation:
-    '''
-    Orientation of diodes on handwired boards. You can think of:
-    COLUMNS = vertical
-    ROWS = horizontal
-    '''
-
-    COLUMNS = 0
-    ROWS = 1
-
 
 class UnicodeMode:
     NOOP = 0