CLASSES/MACHINES: update for v2.0.0

Several updates integrated:
- removal of no more supported basic boot scheme
- removal of no more supported boot device (nor-nand and nor-emmc)
- rework of providers and machine features
- introduction of new board versions (a, c, d, f)
- update of extlinuxconf-stm32mp class to manage multiple board versions
- configure 'extlinux.conf' file to manage PARTUUID to select rootfs
partition
- new partition images management (easy to add or remove partition through
new PARTITIONS_CONFIG var
- specific configuration on machine side for all storage device supported

Change-Id: I7e4d3d16535a5654c7fd80f9b56296a61050def3

recipes-core/base-files/base-files_%.bbappend

@@ -1,4 +1 @@
 FILESEXTRAPATHS_prepend_stm32mpcommon := "${THISDIR}/${PN}:"
-
-dirs755_append_stm32mpcommon = " ${STM32MP_USERFS_MOUNTPOINT_IMAGE}"
-dirs755_append_stm32mpcommon = " ${STM32MP_VENDORFS_MOUNTPOINT_IMAGE}"