The new master branch should point now to rocky.
So, HOT templates should specify that they might contain features
for rocky release 
Also, this submission updates the yaml validation to use only latest
heat_version alias. There are cases in which we will need to set
the version for specific templates i.e. mixed versions, so there
is added a variable to assign specific templates to specific heat_version
aliases, avoiding the introductions of error by bulk replacing the
the old version in new releases.