Investigate Duckdb's Variant support

[friendlymatthew]

DuckDB landed full Variant support recently: https://motherduck.com/blog/DuckDB-1.5-features-I-am-excited-about

Now that we have another standard to compare against, it would be worthwhile to investigate what UDF's they offer + their performance

cc @adriangb @alamb

[adriangb]

If we're still on time one reasonable request would be to try to sync up the APIs (UDF names and arguments) to some extent. It's always nice when the same SQL works in two places.

[sdf-jkl]

https://github.com/duckdb/duckdb/tree/main/src/function/scalar/variant

duckdb	datafusion-variant
variant_extract.cpp	variant_get.rs
variant_normalize.cpp	nothing
variant_typeof.cpp	variant_pretty.rs, but not really
variant_utils.cpp	it's their utils

https://github.com/duckdb/duckdb/tree/main/src/function/cast/variant

duckdb	datafusion-variant
from_variant.cpp	variant_to_arrow?
to_json.cpp	variant_to_json.rs
to_variant.cpp	cast_to_variant.rs

I could add similar tables with databricks/spark functions