Tracking issue for release notes of #124032: Replace sort implementations

[rustbot]

This issue tracks the release notes text for #124032.

• Issue is nominated for the responsible team (and T-release nomination is removed).
• Proposed text is drafted by team responsible for underlying change.
• Issue is nominated for release team review of clarity for wider audience.
• Release team includes text in release notes/blog posts.

Release notes text:

The section title will be de-duplicated by the release team with other release notes issues.
Prefer to use the standard titles from previous releases.
More than one section can be included if needed.

# Compatibility Notes
- [Replace sort implementations](https://github.com/rust-lang/rust/pull/124032)

Release blog section (if any, leave blank if no section is expected):

[workingjubilee]

cc @Voultapher @orlp if you want to have input on the relnotes here.

[joshtriplett]

Sketch for the compatibility aspect (not covering the details of the performance improvement):

The implementations of sort functions (sort, sort_by, sort_by_cached_key, sort_by_key, sort_unstable, sort_unstable_by, sort_unstable_by_key) now have higher performance. These functions may now panic if the implementation of Ord or the supplied comparison function is not a total order.