When AdjustDateTimeStyleFormat determines that no adjustment is needed
(no conflicting fields), the original date/time style pattern should be
used as-is for Temporal type formatting. Previously, the CalendarPattern
was round-tripped through ICU, which apparently can produce a different
pattern than the original result.
Primary motivation for this change is the `VERIFY(icu_success(status))`
line in `Segmenter::create()` that was failing on multiple systems and
where we had to ask people to apply a patch to even know what the error
was.
Since this seems to be a recurring problem, let's just add a little
helper function and print the error codes returned by library calls.
