Improve ICU4X beta2 datetime executor

[sffc]

Not yet completely done, but it brings the number of errors from ~90 down to 12 and successes from 0 to 25.

[sffc]

Also, the input options are something like:

{"locale":"en","input_string":"2000-01-01T00:00:00Z","options":{"timeZone":"Etc/GMT","dateStyle":"short","timeStyle":"full","calendar":"gregory"},"tz_offset_secs":0,"label":"012","original_input":"2000-01-01T00:00Z[Etc/GMT]","dateTimeFormatType":"atTime","hexhash":"7ab8fdbd6793958b9b55a0c11be82098cd3d7581"}

A few issues with this:

1. Doesn't include fields such as time precision, zone style, year style, and alignment
2. It seems arbitrary whether things are in the options or not

[sven-oly]

1. Doesn't include fields such as time precision, zone style, year style, and alignment

• zoneStyle and yearStyle are in the data from CLDR.
• time precision and alignment are not provided now.