`cast_to_variant`: Support casting from more column types

[friendlymatthew]

Currently, cast_to_variant accepts the following arguments:

cast_to_variant(BinaryViewArray, BinaryViewArray) # represents metadata, value columns

I don't see why we can support the following:

cast_to_variant(StringArray | StringViewArray | LargeStringArray) # represents String values

where each str (s) in the array can be converted to a Variant from Variant::from(s)

This applies to other array types like FixedSizeBinaryArray

cast_to_variant(FixedSizeBinaryArray) # represents UUID (FixedSizeBinary(16))

datafusion-variant/src/cast_to_variant.rs

Lines 52 to 62 in 8910c31

	match args.arg_fields.as_slice() {
	[metadata_field, variant_field] => {
	try_field_as_binary(metadata_field.as_ref())?;
	try_field_as_binary(variant_field.as_ref())?;
	}
	_ => {
	// right now, let's only support (BinaryViewArray, BinaryViewArray)
	// but I don't see why we couldn't call cast_to_variant(string_column) -> VariantArray...
	return exec_err!("unsupported, expected 2 arguments");
	}
	}