perf: Half the size of Booleans in row encoding

[coastalwhite]

This changes the encoding of pl.Boolean in the row encoding from needing 2 bytes (1 for validity, 1 for value) to 1 byte. Now, the encoding of Boolean values is as follows:

Value	Encoding
None	0x00
False	0x20
True	0x30

The null is bitwise inverted for nulls_last=True and False / True are inverted for descending=True.

This is a continuation of #19874.

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 58.53659% with 34 lines in your changes missing coverage. Please review.

Project coverage is 59.28%. Comparing base (414d883) to head (7615e2c). Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
crates/polars-row/src/fixed.rs	40.38%	31 Missing :warning:
crates/polars-row/src/row.rs	80.00%	2 Missing :warning:
crates/polars-row/src/variable.rs	50.00%	1 Missing :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #19927 +/- ## ======================================= Coverage 59.28% 59.28% ======================================= Files 1555 1555 Lines 216180 216213 +33 Branches 2456 2456 ======================================= + Hits 128155 128177 +22 - Misses 87467 87478 +11 Partials 558 558 ```

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