Revisit cocoindex data types exported by Python SDK

[badmonster0]

CocoIndex data types: https://cocoindex.io/docs/core/data_types

Problems:

• Types such as cocoindex.typing.Float32 are too long. cocoindex.Float32 is better and easier to use. Same for other types under cocoindex.typing.
• For vector, Annotated[list[type], cocoindex.typing.Vector(dim=N)] is too long and hard to use. Something like cocoindex.Vector[type, N] is better.

We want to:

• Update the Python SDK to allow users to reference these types in easier way.
• Update documents accordingly.
• Update examples accordingly.

[badmonster0]

I'm going to change the following type names and their bindings in Python SDK

• List -> LTable (table whose rows have preserved order determined on creation time). Use list[D] as Python type.
• Table -> KTable (table who has a key column). Use dict[K, D] as Python type.