GH-45366: [C++][Parquet] Set is_compressed to false when data page v2 is not compressed

[mapleFU]

Rationale for this change

Currently, if data page v2 is enabled, is_compressed is always set if Page has compression, however, this can be eliminated if:

1. Page is empty
2. Compression makes page event larger.

What changes are included in this PR?

Enhancement is_compressed setting in column_writer.cc

Are these changes tested?

Yes

Are there any user-facing changes?

No

• GitHub Issue: [C++][Parquet] Allowing is_compressed not set if DataPageV2 enabled #45366

[github-actions]

⚠️ GitHub issue #45366 has been automatically assigned in GitHub to PR creator.

[raulcd]

This is a neat improvement. Thanks @mapleFU ! The last change fixed the segmentation fault on Python. I am ok with this PR but will let other experts review / approve. I am just wondering if we don't add specific tests to validate this new behavior

[wgtmac]

LGTM

[pitrou]

LGTM on the principle, do you want to add a small test for it?

[pitrou]

LGTM, just two minor suggestions

[mapleFU]

Thanks! Would merge after all ci passed

[conbench-apache-arrow]

After merging your PR, Conbench analyzed the 4 benchmarking runs that have been run so far on merge-commit c58ec9c.

There were no benchmark performance regressions. 🎉

The full Conbench report has more details. It also includes information about 4 possible false positives for unstable benchmarks that are known to sometimes produce them.