Previously, the time zone components of date/time literals were ignored.
In order to store the time zone properly for re-formatting,
this change also changes the representation of `Formattable` date
values to use a `GregorianCalendar` rather than a `UDate`.
(This is a public API change.)
This updates the MF2 spec tests to 943479b602 with the following exceptions:
- functions/currency.json and functions/math.json are omitted because these are not yet implemented
- bidi.json will be handled in a future PR
- u-options.json will be handled in a future PR
Changes include:
* `:integer` now returns a value encapsulating the rounded numeric value of the argument, rather than
the value itself.
* Fallbacks are handled according to the current spec.
* Fallback values are not passed into functions.
* Characters inside literal fallbacks are properly escaped.
* The test runner skips null values properly.
* The test runner handles boolean `expErrors` in defaultTestProperties.
* `:string` normalizes its input and normalizeNFC() has been refactored so it can be called there.
Inside of locimp_forLanguageTag() in _appendKeywords() in uloc_tag.cpp
there's a hardcoded special case for "-u-va-posix" which appends the
"_POSIX" variant but this was missed during the refactoring made for
ICU-22520 (there isn't any test case that covers this).
So the call to locimp_forLanguageTag() did more than previously
understood, but we still don't want to have to call that for every
language tag that has BCP-47 extensions just in order to get to this
special case. Instead, add a special case also to ulocimp_getSubtags().
For this to work nicely, the loop in _getVariant() that copies variants
needs to be refactored so that it easily can break when encountering the
start of any BCP-47 extension (which also has the welcome side-effect of
making it more efficient, being able to append an entire variant at once
to the output sink).
This was broken by commit 678d5c1273.
