UInt8 isn't enough for partitioning values

[Igosuki]

Describe the bug
I hit a limitation in the PartitionColumnProjector, when there are too many partition values. Changing dictionary keys to UInt16 made it work.

To Reproduce
Steps to reproduce the behavior:
For instance, I modified the test in parquet_multiple_partitions in module path_partitions like this :

#[tokio::test]
async fn parquet_multiple_partitions() -> Result<()> {
    let mut ctx = ExecutionContext::new();
    let store_paths = (0..200)
        .into_iter()
        .map(|i| {
            format!(
                "first=what/second=ok/year=2021/month={}/day={}/file.parquet",
                i, i
            )
        })
        .collect::<Vec<String>>();
    let store_paths_refs = store_paths
        .iter()
        .map(|s| s.as_str())
        .collect::<Vec<&str>>();
    register_partitioned_alltypes_parquet(
        &mut ctx,
        &store_paths_refs,
        &["first", "second", "year", "month", "day"],
        "",
        "alltypes_plain.parquet",
    )
    .await;

    let result = ctx
        .sql("SELECT id, day FROM t WHERE day=month and first='what' and second='ok' and year='2021' ORDER BY id")
        .await?
        .collect()
        .await?;
    Ok(())
}

At 200 it runs, at 2000 it fails.

Expected behavior
Datafusion shouldn't crash, even for thousands of partition values.

Additional context
I'm using prepartitioned parquet-files to speed up iterating in notebooks

[Igosuki]

P.S. : this is only a fix for 7.0.0, as listing partitions is broken for me on master