Add `to_physical_stream` for lance

[Xuanwo]

This is fine. In a perfect world I think maybe we would have something like...

fn to_physical_stream(&self, stream: SendableRecordBatchStream) -> PhysicalRecordBatchStream;

This way the compiler could make sure that we aren't accidentally using the logical stream in places we should be using the physical stream (or vice-versa).

However, we can think about this as a todo for now.

Originally posted by @westonpace in #5096 (review)