Support `kurtosis_pop` in Aggregation function

[Weijun-H]

Is your feature request related to a problem or challenge?

The excess kurtosis (Fisher’s definition) without bias correction.

Describe the solution you'd like

D SELECT kurtosis_pop(col) FROM VALUES (1), (10), (100), (10), (1) as tab(col);
┌─────────────────────┐
│ kurtosis_pop(col) │
│ double │
├─────────────────────┤
│ 0.19432323191699075 │
└─────────────────────┘

Describe alternatives you've considered

No response

Additional context

https://duckdb.org/docs/sql/functions/aggregates#kurtosis_popx
https://clickhouse.com/docs/en/sql-reference/aggregate-functions/reference/kurtpop

[goldmedal]

take

[alamb]

Given #12357 we may want to move this function to some other repo rather than the core