RAUC update: Use verity bundle format (#2786)

Move from the current plain format to the new verity bundle format. This
requires at least HAOS 10.4 to work. The Supervisor will make sure to
update to the latest minor release of the previous major release, so
updating will work in the regular use case.

buildroot-external/ota/manifest.raucm.gtpl

@@ -2,6 +2,9 @@
 compatible={{ env "ota_compatible" }}
 version={{ env "ota_version" }}
 
+[bundle]
+format=verity
+
 [hooks]
 filename=hook
 hooks=install-check;