GH-49415: [C++] Don't change map type key/item/value field names #5509

Job	Run time
check-labels / Check labels	29s
ODBC ${{ matrix.architecture }} macOS ${{ matrix.macos-version }}	0s
ARM64 Windows 11 MSVC	0s
matrix.title	0s
ODBC Windows	0s
JNI ${{ matrix.platform.runs-on }} ${{ matrix.platform.arch }}	0s
JNI macOS	0s
ODBC release	0s
ODBC nightly	0s
report-extra-cpp	0s
	29s

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