[C++] Support cast from timestamp[UTC] to string on Windows

[asfimport]

As per ARROW-13168 we lack tzdb on Windows and so many operations on timestamp with timezone are not implemented. However, many of them could be implemented for the special case of UTC, e.g. casting timestamp[s, UTC] to string on Windows could be implemented without needing tzdb.

Follow up to ARROW-14231.

Reporter: David Li / @lidavidm

Related issues:

• [C++] Timezone database configuration and access (relates to)
• [C++] Can't cast from timestamp to utf8 when saving CSV (relates to)

_{Note: This issue was originally created as ARROW-14643. Please see the migration documentation for further details.}