CLDR-17282 Add currency attributes tz, to-tz and docs; use for currency changes from 2022-01-01

[pedberg-icu]

CLDR-17282

• This PR completes the ticket.

1. For the currency element, add attributes tz and to-tz. Document these in the spec, along with note that implementations may want to convert the combination of date time and timezone to a UTC timestamp or equivalent for use as runtime data.

   • I made these @VALUE since they are not distinguishing attributes (but rather annotations for the to and from attributes); however they are not really like element values either. I also updated PathHeader accordingly.

2. Update the supplemental currency data to use these new attributes for all currency transitions from 2022-01-01 onward. There were only two, for Croatia using tz Europe/Zagreb, and for Sierra Leone, using tz Africa/Freetown. Both of those zones are currently aliases in the backward file, but are still valid in CLDR I believe.

3. I have filed ICU-22631 for the associated work in the cldr-icu converter.

ALLOW_MANY_COMMITS=true

[srl295]

LGTM. Only comment is if 'IANA timezone' should actually be CLDR timezone, including aliases and such.

[pedberg-icu]

LGTM. Only comment is if 'IANA timezone' should actually be CLDR timezone, including aliases and such.

Thanks, I will investigate and file another PR against the same ticket if it needs changing.

[pedberg-icu]

LGTM. Only comment is if 'IANA timezone' should actually be CLDR timezone, including aliases and such.

Thanks, I will investigate and file another PR against the same ticket if it needs changing.

@srl295 OK, PR #3468 changes the timezone ID specification to specifically reference the CLDR canonical “long” time zone ID.