[intl] Add support for adding and removing likely subtags for a locale, as defined in UTS#35

[stof]

Description

UTS#35 has algorithms to add or remove likely subtags for a locale. This is useful for instance when wanting to use \Locale::getScript to get the script associated with a locale, to get the likely script instead of getting null when the locale string does not specify a script explicitly.

ICU4X (the Rust implementation of ICU) has a LocaleExpander class with maximize and minimize methods: https://unicode-org.github.io/icu4x/rustdoc/icu/locale/struct.LocaleExpander.html (their implementation mutates the identifier object in place and returns an info about whether it was modified or no, but the PHP implementation should likely return the new string instead as PHP does not use objects for language identifiers anyway).
ICU4C has functions uloc_addLikelySubtags and uloc_minimizeSubtags

It would be great to expose this ICU capability to PHP code.

[youkidearitai]

Thank you very much for feature request. Seems need this. Just a moment please.

[devnexen]

@youkidearitai I can have a look unless you really want to do it yourself, since it is related to this feature.