[Parquet] How to decode part columns of ColumnIndex

**Which part is this question about**

New parquet metadata decoder and page index. I know we have https://github.com/apache/arrow-rs/issues/8643 , and we can avoid Statistics via https://github.com/apache/arrow-rs/blob/main/parquet/src/file/metadata/options.rs#L91
but column index seems follow a different rule: https://github.com/apache/arrow-rs/blob/main/parquet/src/file/metadata/parser.rs#L244

I may miss the reason here.

**Describe your question**

How can we avoid decode some columns in column index

**Additional context**

No

Start by reading the referenced code in parquet/src/file/metadata/options.rs and parquet/src/file/metadata/parser.rs, then review issue 8643 for the related metadata-decoding context. Compare how Statistics and ColumnIndex are decoded and establish the intended rule for skipping columns; done means the expected behavior is clarified well enough to guide an implementation.

Written by the indexing model from the issue text.