Ritchie Vink

### Problem description Can use quick-select

### Problem description evaluate `is_first` for `struct` dtypes.

WIP

The goal is to replace the current Arrow (Large)String type with a string type that allows a union between an inlined small string and an offset to a string that...

### Description This is probably the most executed query on large datasets. We materialize here where we shouldn't. For `parquet` and `ipc` we can use metadata. For `csv` and `(nd)json`...

Ensure that the parquet types always get converted to polars supported data-types. Before this, deeply nested datatypes were still of the wrong type, leading to unneeded casts. All code increase...

The great migration of the string/binary type. All preliminary work is done. This is the final push of #13459

perf: radix partitioning in single key group-by

1

We did a full scan per thread to do radix partitioning. This adds a repartition phase that scatters the keys. Will follow up with benchmarks.

:crossed_fingers: