arrow

GH-44714: [C++] Keep field metadata for keys and values when importing a map type via the C data interface (#44715)

### Rationale for this change

Import of a map type from the C data interface drops field metadata (including extension type information) which does not happen when importing a map type from IPC or a list of structs. This affects the ability to roundtrip data through pyarrow/Arrow C++ if extension types are not registered.

### What changes are included in this PR?

The mechanism to import the map type was changed to align with the method used for IPC import.

### Are these changes tested?

Yes.

### Are there any user-facing changes?

The current behaviour was surprising/inconsistent, so I think this PR brings it in more line with the current expectation/documentation.
* GitHub Issue: #44714

Authored-by: Dewey Dunnington <dewey@voltrondata.com>
Signed-off-by: Antoine Pitrou <antoine@python.org>