Ensure that the provider performs correct non-Chinese collation alias mapping

[hsivonen]

Ensure that the provider is performs these alias mappings from CLDR for collations (Traditional Chinese and Norwegian have more specific issues):

pa_IN: pa_Guru_IN sr_RS: sr_Cyrl_RS ars: ar_SA in_ID: id_ID iw: he in: id mo: ro sh_YU: sr_Latn_RS sh: sr_Latn sr_ME: sr_Cyrl_ME sh_BA: sr_Latn_BA sh_CS: sr_Latn_RS sr_BA: sr_Cyrl_BA iw_IL: he_IL

[hsivonen]

CC @sffc.

Norwegian: #1963. Traditional Chinese: #1964.

[hsivonen]

Looks like these aliases exist as JSON.

[sffc]

We'll do mappings according to likely subtags and parent locales by default:

• https://github.com/unicode-org/icu4x/blob/main/provider/testdata/data/cldr/cldr-core/supplemental/likelySubtags.json
• https://github.com/unicode-org/icu4x/blob/main/provider/testdata/data/cldr/cldr-core/supplemental/parentLocales.json

My proposed policy for legacy subtags (aliases) is that developers should call LocaleCanonicalizer::canonicalize before passing the locale into ICU4X.

• https://github.com/unicode-org/icu4x/blob/main/provider/testdata/data/cldr/cldr-core/supplemental/aliases.json

[sffc]

The source for these mappings is:

https://github.com/unicode-org/icu/blob/main/tools/cldr/cldr-to-icu/build-icu-data.xml#L263

#2506 lays the groundwork for this to work. I will add tests for this iteratively.

[sffc]

I'm using this as the main tracking issue for collation fallbacks.