Refactor: scheduler: Expose native_output_string as pcmk__native_output_string.
    
    The plan is that this function can be used to help build the string that
    is output for each line of "crm_resource -o" output.  It appears that
    output only happens for primitive resources.  However, I've added a
    check at the beginning just in case it's called for some other type of
    resource.
    
    patch_name: 004-feature-set.patch
    present_in_specfile: true
    location_in_specfile: 4
    squash_commits: true