GH-48846: [C++] Read message metadata and body in one go in IPC file reader #5254

Job	Run time
check-labels / Check labels	28s
ARM64 Windows 11 MSVC	0s
ODBC ${{ matrix.architecture }} macOS ${{ matrix.macos-version }}	0s
JNI ${{ matrix.platform.runs-on }} ${{ matrix.platform.arch }}	0s
ODBC Windows	0s
JNI macOS	-1s
ODBC nightly	-1s
ODBC release	-1s
report-extra-cpp	-1s
matrix.title	-1s
	23s

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