demo - force group positions to match AggState

[nameexhaustion]

This PR forces GroupPositions to match AggState within AggregationContext.

In doing so, multiple queries will fail - e.g.

>>> df = pl.DataFrame({"a": [1, 1, 2, 2, 3], "b": [1, 2, 1, 2, 1]})
>>> df.group_by(pl.lit(1)).agg(a=pl.col("a").first().filter(pl.col("b") >= 0))

• Expected results

shape: (1, 2)
┌─────────┬─────────────┐
│ literal ┆ a           │
│ ---     ┆ ---         │
│ i32     ┆ list[i64]   │
╞═════════╪═════════════╡
│ 1       ┆ [1, 1, … 1] │
└─────────┴─────────────┘

• Results from this PR

shape: (1, 2)
┌─────────┬───────────┐
│ literal ┆ a         │
│ ---     ┆ ---       │
│ i32     ┆ list[i64] │
╞═════════╪═══════════╡
│ 1       ┆ [1]       │
└─────────┴───────────┘

[github-actions]

The uncompressed lib size after this PR is 52.4220 MB.