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GH-45227: [C++][Parquet] Enable Size Stats and Page Index by default (#45249)

### Rationale for this change

Benchmark data shows that enabling page index and size stats by default does not have significant penalty.

### What changes are included in this PR?

Enable the parquet writer to generate page index and size stats by default.

### Are these changes tested?

Pass CIs.

### Are there any user-facing changes?

No.
* GitHub Issue: #45227

Authored-by: Gang Wu <ustcwg@gmail.com>
Signed-off-by: Gang Wu <ustcwg@gmail.com>