Update meta layers to new override syntax

Bitbake has changed to a new override syntax using colons instead of underscores exclusively. (https://lists.openembedded.org/g/bitbake-devel/topic/patch_1_4_bitbake_switch/84550184?p=,,,20,0,0,0::recentpostdate%2Fsticky,,,20,2,0,84550184)

All of our meta layers (meta-boot2qt, meta-qt6, meta-qt5) will need to be converted to the new syntax, if the Yocto version 3.4 (Honister) or later are used.