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ARROW-14999: [C++] Optional field name equality checks for map and list type (#14847)

BREAKING CHANGE

Two changes for "internal fields" (fields within ListTypes and MapTypes):

 * ListType and MapType internal field names only matter in comparisons when `check_metadata` is `true`.
 * Nullability of MapType internal fields now matters in comparison.

Lead-authored-by: Will Jones <willjones127@gmail.com>
Co-authored-by: Antoine Pitrou <pitrou@free.fr>
Signed-off-by: Antoine Pitrou <antoine@python.org>