Auto merge of #51750 - zackmdavis:superstructure, r=oli-obk

three diagnostics upgrades

 * reword `...` expression syntax error to not imply that you should use it in patterns either (#51043) and make it a structured suggestion
 * shorten the top-line message for the trivial-casts lint by tucking the advisory sentence into a help note
 * structured suggestion for pattern-named-the-same-as-variant warning

r? @oli-obk