Support multi bucket layout

[jaystarshot]

Currently entire lance dataset needs to be in one bucket. We should add a multi bucket layout support. That way indices, manifest and data can be stored in separate locations (maybe separate filesystems)

[jackye1995]

As a part of shallow clone and branching, we added the idea of base_paths. I think that can fit your need, and all the mechanics are already built in the SDK to properly read and write data, deletion and index files with different base paths.

I think we just need to maybe expose the right APIs for your use case of multi-bucket setup.

See: https://github.com/lancedb/lance/blob/main/protos/table.proto#L155-L164