Consider using script fallback for time zone names and maybe others

[sffc]

The data size optimization landed in #5751 reduces data size in English and other Latin-script languages, but it has minimal impact on other languages.

To reduce this bias, should we consider having a und-Script locale for time zone names. It can contain the names in the language according to likely subtags. This may help languages that share a script, such as sr/uk/ru or zh/zh-Hant/yue. Spot-checking, there are definitely display name overlaps in those languages.

@robertbastian