x/text/internal/language: Script overflows during generation

[rolandshoemaker]

The IANA Language Subtag Registry contains more than 256 scripts, causing the generated script indices to overflow the Script type. Bumping it to uint16 seems reasonable.

cc @mpvl

[gopherbot]

Change https://golang.org/cl/304029 mentions this issue: internal/language: bump script types to uint16 and update registry

[esote]

@rolandshoemaker @neild @josharian @mpvl Any update on the open CL? This issue is blocking #51822 for tagging a new x/text release, which is blocking x/text support for generics #52553. Seems like the size increase discussion was resolved?