feat(usb): Add boot protocol support

* USB boot protocol support
* Use a single definition of a boot report, used for regular reports in
  non-6KRO, and for rollover in all branches.
* Handle gaps in the zmk report when producing a boot report in HKRO mode. For
  .example, if it was 8KRO, it would be possible to have the state 0 0 0 0 0 0 0
  17 (by pressing 8 keys, and letting go of the first 7). Copying the first 6
  bytes would not show up the single pressed key.
* Disable usb status change and callback on SOF events:
  SOF events were introduced by the boot protocol changes, and required internally
  by Zephyr's idle support, but are unused within ZMK itself. Ignore them in the
  usb status callback.

---------

Co-authored-by: Andrew Childs <lorne@cons.org.nz>

app/Kconfig

@@ -103,6 +103,11 @@ config USB_NUMOF_EP_WRITE_RETRIES
 config USB_HID_POLL_INTERVAL_MS
     default 1
 
+config ZMK_USB_BOOT
+    bool "USB Boot Protocol Support"
+    default y
+    select USB_HID_BOOT_PROTOCOL
+    select USB_DEVICE_SOF
 #ZMK_USB
 endif
 
@@ -575,4 +580,3 @@ osource "$(ZMK_CONFIG)/boards/shields/*/Kconfig.shield"
 
 
 source "Kconfig.zephyr"
-