Is your feature request related to a problem or challenge? Please describe what you are trying to do.
I ran into this while working on the benchmark here

• Measure best case performance for the new thrift-remodel / custom thrift parser #8441

I noticed a substantial amount of time (15% of the overall time) in the benchmark was spent in convert_row_groups

Describe the solution you'd like
I think that code could likely be optimized.

Describe alternatives you've considered
Two obvious candidates:

1. Use the into_iter() / collect pattern to map the results (which is highly optimized in Rust)
2. Don't clone the Arc<SchemaDescriptor> -- I think it only needs a reference

Another thing would be to decode directly into RowGroupMetaData somehow (maybe make RowGRoupMetaData a view on an inner RowGroup 🤔

struct RowGroupMetaData {
  inner: RowGroup
}

Additional context