ConvertDownwardAPIFieldLabel converts the specified downward API field label
and its value in the pod of the specified version to the internal version,
and returns the converted label and value. This function returns an error if
the conversion fails.
VisitContainersWithPath invokes the visitor function with a pointer to the spec
of every container in the given pod spec and the field.Path to that container.
If visitor returns false, visiting is short-circuited. VisitContainersWithPath returns true if visiting completes,
false if visiting was short-circuited.