GH-49697: [C++][CI] Check IPC file body bounds are in sync with decoder outcome

[pitrou]

Rationale for this change

When we read an IPC message from an IPC file, we validate its associated body size against the amount required by the streaming decoder. However, we're currently only checking that the body size is large enough, not that it's exactly as expected.

An invalid IPC file might advertise in its footer a metaDataLength that's larger than the actual serialized Flatbuffers payload. In that case, the associated body would start before the offset computed from the IPC file footer.

What changes are included in this PR?

1. Strengthen body size check against expected decoder read, to ensure that the metadata length advertised in the IPC file footer is consistent with the actual size of the Flatbuffers-serialized metadata.
2. Refactor RecordBatch IPC loading to reduce code duplication.
3. (as a consequence of item 2 above) Fix latent bug where the IPC file reader did not apply the ensure_alignment option to buffers read from IPC.

Are these changes tested?

By additional fuzz regression file.

Are there any user-facing changes?

No.

• GitHub Issue: [C++] Check IPC file body bounds are in sync with decoder outcome #49697

[pitrou]

@github-actions crossbow submit -g cpp

[pitrou]

@github-actions crossbow submit -g cpp

[github-actions]

Revision: 3b2d101

Submitted crossbow builds: ursacomputing/crossbow @ actions-265034e4bd

Task	Status
example-cpp-minimal-build-static
example-cpp-minimal-build-static-system-dependency
example-cpp-tutorial
test-build-cpp-fuzz
test-conda-cpp
test-conda-cpp-valgrind
test-debian-13-cpp-amd64
test-debian-13-cpp-i386
test-debian-experimental-cpp-gcc-15
test-fedora-42-cpp
test-ubuntu-22.04-cpp
test-ubuntu-22.04-cpp-20
test-ubuntu-22.04-cpp-bundled
test-ubuntu-22.04-cpp-emscripten
test-ubuntu-22.04-cpp-no-threading
test-ubuntu-24.04-cpp
test-ubuntu-24.04-cpp-bundled-offline
test-ubuntu-24.04-cpp-gcc-13-bundled
test-ubuntu-24.04-cpp-gcc-14
test-ubuntu-24.04-cpp-minimal-with-formats
test-ubuntu-24.04-cpp-thread-sanitizer

[pitrou]

@lidavidm Could you perhaps take a look?

[pitrou]

@raulcd This may be a good last-minute fix for 24.0.0.

[conbench-apache-arrow]

After merging your PR, Conbench analyzed the 3 benchmarking runs that have been run so far on merge-commit 982797c.

There were no benchmark performance regressions. 🎉

The full Conbench report has more details. It also includes information about 2 possible false positives for unstable benchmarks that are known to sometimes produce them.