fix: remove unsupported type casting in integer vector handling

[lemorage]

In #595 and #586, we added support for numeric types in numpy array annotations. np.uint types and np.int32 were included even though in cocoindex data types we could only handle Int64, Float64 and Float32. We achieved this by type casting.

This PR attempts to remove the casting, and only supports np.int64, np.float64 and np.float32 for consistency.

Relevant proposal: #586 (comment)

[badmonster0]

Thanks a lot!