arrow

GH-37934: [Doc][Integration] Document C Data Interface testing (#37935)

### Rationale for this change

gh-37537 added integration testing for the C Data Interface, but the documentation was not updated.

### What changes are included in this PR?

Add documentation for C Data Interface integration testing.

### Are these changes tested?

N/A, only doc changes.

### Are there any user-facing changes?

No.
* Closes: #37934

Authored-by: Antoine Pitrou <antoine@python.org>
Signed-off-by: Antoine Pitrou <antoine@python.org>