Use parquet metadata in /rows
Step 2 of https://github.com/huggingface/datasets-server/issues/1186

## Implementation details

I implemented ParquetIndexWithMetadata (new) and ParquetIndexWithoutMetadata (from the existing code).:

- ParquetIndexWithMetadata is used when `config-parquet-metadata` is cached and is fast
- ParquetIndexWithoutMetadata is the old code, that runs when `config-parquet-metadata` is not available yet

I think in the long run we should remove ParquetIndexWithoutMetadata. I just kept it so that the UI doesn't show an error when `config-parquet-metadata` is not available.

I re-added support for image and audio for the ParquetIndexWithMetadata
Use parquet metadata in /rows: Step 2 of https://github.com/huggingface/datasets-server/issues/1186

## Implementation details

I implemented ParquetIndexWithMetadata (new) and ParquetIndexWithoutMetadata (from the existing code).:

- ParquetIndexWithMetadata is used when `config-parquet-metadata` is cached and is fast
- ParquetIndexWithoutMetadata is the old code, that runs when `config-parquet-metadata` is not available yet

I think in the long run we should remove ParquetIndexWithoutMetadata. I just kept it so that the UI doesn't show an error when `config-parquet-metadata` is not available.

I re-added support for image and audio for the ParquetIndexWithMetadata