Backport Unicode updates?

[Florian Weimer]

* Naïm Favier via Libc-stable:

> It would be nice to backport Unicode updates (and more generally
> changes to locale data, I guess) to release branches, so that
> distributions can include them more quickly. See
> https://github.com/weechat/weechat/issues/79,
> https://github.com/NixOS/nixpkgs/issues/202548 for more context.
>
> For example, could the Unicode 15 support in 7fe6734d28 be
> backported to the stable 2.36 (and maybe 2.35) branches without
> breaking anything?

Changes to collation order and case conversion have broken on-disk
data structures in the past (such as B-tree indices for PostgreSQL).
So it's not risk-free.