unicode: update to Unicode 16.0.0

[cowtoolz]

Upgrade all of the versioned Unicode code to use new code generated for the current version 16.0.0, released September 10, 2024. Go is currently on Unicode v15.0.0

Closes #65141

[prattmic]

cc @golang/security @robpike

[rolandshoemaker]

This doesn't seem like an easy upgrade. Simply running UNICODE_VERSION=16.0.0 go generate fails, seemingly due to the introduction of some new scripts that have complex layouts that we don't properly handle in unicode/norm/maketables.go.

I do not have a firm enough grasp of Unicode to understand how this would be fixed.

[rolandshoemaker]

In particular it seems like we will need to do something about https://www.unicode.org/reports/tr15/tr15-56.html#Contexts_Care.

[cowtoolz]

@rsc seems to be actively doing some related work #70780

[seankhliao]

unicode 17 is out now https://www.unicode.org/versions/Unicode17.0.0/

[robpike]

We should skip 16 and update to 17, and do if for the pending release. We are two Unicode versions behind and the update process shouldn't be too hard.

[robpike]

Probably too late for 26..0 but how about 26.1? It's wrong to be so far behind.

[rolandshoemaker]

@robpike see https://go.dev/cl/704675 for a discussion of the problems we've run into when trying to update to 16. I suspect we'll have the same problems with 17 due to the new scripts, and their semantics, that were introduced in 16. There is no obvious immediate solution to this that I'm aware of.

[rolandshoemaker]

Whoops, https://go.dev/cl/704675.

[robpike]

https://go-review.googlesource.com/c/go/+/737420