i.MX6UL/ULL U-Boot Upgrade v2022.10

This MR is similar to !35 (merged) for i.MX8MM boards.
It provides a new U-Boot version (2022.10) for the i.MX6UL/ULL boards. The new version is in sync with mainline U-Boot.

Status: tested on BL i.MX6UL

• Instead of a separate U-Boot Environment, use u-boot-initial-env in Userspace (for SWUpdate/libubootenv)
• Overwrite the board's environment text file in the U-Boot source tree to add vendor-specific boot scripts for A/B boot
  • The provided environment contains scripts from the U-Boot standard distro boot and vendor-specific scripts prefixed with vendor_
  • To use standard distro boot flow (extlinux, etc.) do setenv bootcmd distro_bootcmd
  • To use vendor boot flow (SWUpdate) do setenv bootcmd vendor_bootcmd
• Instead of handling SPL and U-Boot proper separately, use the combined flash.bin file created by U-Boot (binman)
  • This also affects the SPI NOR MTD partitions which have already been adjusted in the kernel
• Add a recipe for v2022.10 and switch all KTN i.MX6UL/ULL boards to use it as default
• Keep 2020.01 recipe for customer projects that still use it and haven't been upgraded yet