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/hid.py

@@ -1,10 +1,44 @@
 import usb_hid
 
-from kmk.consts import HID_REPORT_SIZES, HIDReportTypes, HIDUsage, HIDUsagePage
 from kmk.keys import FIRST_KMK_INTERNAL_KEY, ConsumerKey, ModifierKey
 
 
-class USB_HID:
+class HIDModes:
+    NOOP = 0  # currently unused; for testing?
+    USB = 1
+    BLE = 2  # currently unused; for bluetooth
+
+    ALL_MODES = (NOOP, USB, BLE)
+
+
+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
+
+
+HID_REPORT_SIZES = {
+    HIDReportTypes.KEYBOARD: 8,
+    HIDReportTypes.MOUSE: 4,
+    HIDReportTypes.CONSUMER: 2,
+    HIDReportTypes.SYSCONTROL: 8,  # TODO find the correct value for this
+}
+
+
+class AbstractHID:
     REPORT_BYTES = 8
 
     def __init__(self):
@@ -154,7 +188,7 @@ class USB_HID:
         return self
 
 
-class CircuitPythonUSB_HID(USB_HID):
+class USBHID(AbstractHID):
     REPORT_BYTES = 9
 
     def post_init(self):
@@ -187,3 +221,10 @@ class CircuitPythonUSB_HID(USB_HID):
         return self.devices[reporting_device_const].send_report(
             evt[1 : HID_REPORT_SIZES[reporting_device_const] + 1]
         )
+
+
+class BLEHID(AbstractHID):
+    def __init__(self, *args, **kwargs):
+        raise NotImplementedError(
+            'BLE HID is not supported by upstream CircuitPython yet'
+        )