Support `map_keys` function for Map type

[Weijun-H]

Is your feature request related to a problem or challenge?

Description	Return a list of all keys in the map.
Example	map_keys(map([100, 5], [42,43]))
Result	[100, 5]

Describe the solution you'd like

No response

Describe alternatives you've considered

No response

Additional context

https://docs.databricks.com/en/sql/language-manual/functions/map_keys.html#map_keys-function https://duckdb.org/docs/sql/functions/map.html#map_keysmap

[dharanad]

take