All in-tree uses of MICROPY_PORT_ROOT_POINTERS have been replaced with
MP_REGISTER_ROOT_POINTER(), so now we can remove both
MICROPY_PORT_ROOT_POINTERS and MICROPY_BOARD_ROOT_POINTERS from the code
and remaining config files.
Signed-off-by: David Lechner <david@pybricks.com>
7e4b205cb0