[* DateTimeV2] Refactor Holiday resolution logic to improve defintion re-use across cultures

[tellarin]

Move common holiday definitions and concrete dates to common resources BaseDateTime.yaml and BaseHolidayParserConfiguration, if the same for all supported cultures.

International/standard holidays could be moved to the Base resources/parsers and that just country/language specific holidays should live in the {Locale}HolidayParserConfiguration files.

HolidayParserGer should also be removed and resolution be merged into the regular shared framework.

[tellarin]

This should also include #2660 in non-CJK languages.