move py.typed to correct places

https://peps.python.org/pep-0561/ says 'For namespace packages (see PEP 420), the py.typed file should be in the submodules of the namespace, to avoid conflicts and for clarity.'. Previously, when I added the py.typed file to this project, #382 , I was unaware this was a namespace package. As PEP 561 warns us, this does create conflicts; other libraries in the databricks namespace package (such as, in my case, databricks-vectorsearch) are then treated as though they are typed, which they are not. This commit moves the py.typed file to the correct places, the submodule folders, fixing that problem.

Author: wyattscarpenter