[Parquet] Support leaf-to-index for parquet rust schema descriptor

**Is your feature request related to a problem or challenge? Please describe what you are trying to do.**

The C++ library has a hash map to map column index based on column node path. We'd like to do similar for Rust.

**Describe the solution you'd like**

**Describe alternatives you've considered**

**Additional context**

Start by locating the Rust Parquet schema descriptor and comparing it with the C++ library's hash map for column indexes and column node paths. Confirm how leaf columns are represented, then define completion as supporting the equivalent leaf-to-index lookup in Rust; the issue provides no named files or tests.

Written by the indexing model from the issue text.