bug: round trip FixedSizeList lance <-> arrow. nullability is not preserved

[universalmind303]

round tripping native lance Field from ArrowField and back drops the nullable field.

let arrow_field = ArrowField::new_fixed_size_list(
    "list",
    ArrowField::new("item", DataType::Int32, false),
    1,
    false,
);
let field = Field::try_from(&arrow_field).unwrap();

assert_eq!(field.name, "list");
assert_eq!(field.nullable, arrow_field.is_nullable());
assert_eq!(&field.data_type(), arrow_field.data_type());
assert_eq!(ArrowField::from(&field), arrow_field);

it seems that we drop it because Field::data_type calls impl TryFrom<&LogicalType> for DataType, which hard codes the nullable field.

[wjones127]

Yeah the underlying problem is that when we implemented FixedSizeList data type, we decided not to make the inner field an actual field. It just serialized the data type, and doesn't handle any metadata, nullability, or child fields. This also blocks #1293

I started to fix this in #1693, but it causes drastic breaking changes in how schemas and page tables are handled.

[universalmind303]

I started to fix this in #1693, but it causes drastic breaking changes in how schemas and page tables are handled.

is it possible to do this in a backwards compatible way?