Integrate meta-guf-distro/fng-install-AB-partition-labels

Commit: https://gitlab.com/SECO-Northern-Europe/yocto/layers/meta-guf-distro/-/commit/3469833ea174ad7ac50e83bb943a44624c565705

fng-install: Modify fs labels according to A/B, pass bootpartition to postinsts

The labels for a 'B' installation are adapted to LINUXB and ROOTFSB.

The fngpostinstallation gets called with BOOTPARTITION env variable set to the correct bootpartition.

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Commit: https://gitlab.com/SECO-Northern-Europe/yocto/layers/meta-guf-distro/-/commit/4222a78495bd83a0460e850d5f84e6b77c146c6b

fng-install: Add --AB-target parameter to explicitly install to B, default to A

Removed autodetection of the target for now, use A when not specified.

BCS 746-000634