GH-48799: [C++] Improve SharedExclusiveChecker error messages #4265

Job	Run time
check-labels / Check labels	27s
JNI macOS	0s
JNI ${{ matrix.platform.runs-on }} ${{ matrix.platform.arch }}	-1s
matrix.title	-1s
report-extra-cpp	-1s
ARM64 Windows 11 MSVC	-1s
ODBC	-1s
	22s

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