converter/adb_usb Configurator support and adb_usb.h cleanup (#4348)

converter/adb_usb Configurator support and adb_usb.h cleanup (#4348)

* converter/adb_usb: Configurator support

Note: LAYOUT_ext_ansi has a blank space between the Spacebar and the
Right Alt/Option key when loaded in the Configurator. This is
deliberate.

Stock Apple Extended Keyboards and AEK IIs send the scan code for Left
Command when either Command key is used. (This is noted already in the
readme.) That being the case, the Command keys cannot be assigned to
different functions. Whichever keycode is placed on Left Command will be
used for both Command keys.

* converter/adb_usb: adb_usb.h cleanup

- replaced KEYMAP_COMMON_H with ADB_USB_H
- white space changes for visual alignment in LAYOUT_ext_ansi macro