Add support for variable length arrays

[rmorshea]

Variable length arrays now have dedicated support via tuples:

class MyModel(CModel):
    # bounded at runtime by a count field
    bounded_len_array_count: int
    bounded_len_array: Annotated[tuple[int, ...], CCountField.template("{}_count")]
    # unbounded length
    unbounded_len_array: tuple[in, ...]