Fixes T11249. From what I can tell, the locale tree for Chinese looks like this in modern usage (maybe?):
- zh_Hans Chinese (Simplified)
- zh_ZH Chinese (Simplified, China)
- zh_SG Chinese (Simplified, Singapore)
- zh_Hant Chinese (Traditional)
- zh_TW Chinese (Traditional, Taiwan)
- zh_HK Chinese (Traditional, Hong Kong)
Except that everyone disagrees and does different things and various standards define esoteric things like "zh-Hans-SG".
But I think inheriting them like this mostly makes sense, probably.
This just adds the base locales; we can add the child locales later to distinguish regional variance like "color" vs "colour".