Descending sort of boolean series flips number of trues and falses

[wence-]

Checks

• I have checked that this issue has not already been reported.
• I have confirmed this bug exists on the latest version of Polars.

Reproducible example

use polars::prelude::*;

fn main() -> Result<(), PolarsError> {
    let df = df!("a" => &[true, false, false, false])?.lazy();
    let expr = col("a").sort(SortOptions::default().with_order_descending(true));
    let expect = df.clone().collect()?;
    let got = df.clone().select([expr.clone()]).collect()?;
    println!("Got\n{}", &got);
    println!("Expect\n{}", &expect);
    Ok(())
}

Log output

run ProjectionExec

Issue description

The logic for flipping the order in BooleanChunked.sort_with looks a bit suss.

Probably this is needed:

diff --git a/crates/polars-core/src/chunked_array/ops/sort/mod.rs b/crates/polars-core/src/chunked_array/ops/sort/mod.rs
index c2ef58a23c..5bcbbe0086 100644
--- a/crates/polars-core/src/chunked_array/ops/sort/mod.rs
+++ b/crates/polars-core/src/chunked_array/ops/sort/mod.rs
@@ -610,10 +610,10 @@ impl ChunkSort<BooleanType> for BooleanChunked {
             let len = self.len();
             let n_set = self.sum().unwrap() as usize;
             let mut bitmap = MutableBitmap::with_capacity(len);
-            let (first, second) = if options.descending {
-                (true, false)
+            let (first, second, n_set) = if options.descending {
+                (true, false, len - n_set)
             } else {
-                (false, true)
+                (false, true, n_set)
             };
             bitmap.extend_constant(len - n_set, first);
             bitmap.extend_constant(n_set, second);

Expected behavior

Got
shape: (4, 1)
┌───────┐
│ a     │
│ ---   │
│ bool  │
╞═══════╡
│ true  │
│ true  │
│ true  │
│ false │
└───────┘
Expect
shape: (4, 1)
┌───────┐
│ a     │
│ ---   │
│ bool  │
╞═══════╡
│ true  │
│ false │
│ false │
│ false │
└───────┘

Installed versions

``` [package] name = "polars-doodles" version = "0.1.0" edition = "2021"

[dependencies]
polars = { version = "0.41.3", features = ["lazy"] }
polars-plan = { version = "0.41.3"}

</details>

[mcrumiller]

Can confirm. Simpler python example:

>>> pl.Series([True, False, False]).sort(descending=True)
shape: (3,)
Series: '' [bool]
[
        true
        true
        false
]

The logic is a very simple fix here. The result returns the number of False items first, regardless of descending param.