Rollup merge of #128273 - Voultapher:improve-ord-violation-help, r=workingjubilee

Improve `Ord` violation help

Recent experience in #128083 showed that the panic message when an Ord violation is detected by the new sort implementations can be confusing. So this PR aims to improve it, together with minor bug fixes in the doc comments for sort*, sort_unstable* and select_nth_unstable*.

Is it possible to get these changes into the 1.81 release? It doesn't change behavior and would greatly help when users encounter this panic for the first time, which they may after upgrading to 1.81.

Tagging `@orlp`

Author: GuillaumeGomez