docs(releases): the 18.0.0 notes and upgrade checklist, walked from 17.7.0; Upgrading's table gains 18.0.0 and 17.5–17.7

docs(releases): the 18.0.0 notes and upgrade checklist, walked from 17.7.0; Upgrading's table gains 18.0.0 and 17.5–17.7 #15712