OPENTHREAD_CONFIG_CHILD_SUPERVISION_OLDER_VERSION_CHILD_DEFAULT_INTERVAL macro

@def OPENTHREAD_CONFIG_CHILD_SUPERVISION_OLDER_VERSION_CHILD_DEFAULT_INTERVAL Specifies the default supervision interval to use on parent for children that do not explicitly indicate their desired supervision internal (do not include a "Supervision Interval TLV") and are running older Thread versions (version <= 1.3.0). This config is added to allow backward compatibility on parent with SED children that used Child Supervision feature in OT stack before adoption of it by Thread specification and addition of the "Supervision Interval TLV" as the mechanism for child to inform the parent of its desired supervision interval. The config can be set to zero to effectively disable it, i.e., if a child does not provide "Supervision Interval TLV" it indicates that it does not want to be supervised and then parent will use zero interval for the child.