PARQUET-2172: [C++] Change field return type to const NodePtr& (#13865)
PARQUET-2172: [C++] Change field return type to const NodePtr& (#13865)

Authored-by: emkornfield <dbc64ab8a675880673029ed6b2cb1d084dfef0bb@gmail.com>
Signed-off-by: Yibo Cai <e732a3f0de35687e82bda0008a72e443d2f69704@arm.com>
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