glean might report incomplete/misleading `locale` in `client_info`

[l-hedgehog]

In certain Huawei devices shipped in mainland China, when an user choose Traditional Chinese in its OS settings, the system locale as returned from Locale.getDefault() is zh-Hant-CN.

With such a system setting zh-TW strings would be displayed if available, while glean would still report it as zh-CN.

I think this is the result of unconditional omission of the script subtag in the getLocaleTag function.

[Dexterp37]

Hi @l-hedgehog , thanks for filing this. I filed this bug on bugzilla.