Make the tensor documentation more visible on documentation home page

[diptorupd]

The API documentation for dpctl.tensor is buried under API Documentation -> dpctl -> Submodules -> dpctl.tensor on the documentation site. The organization makes it hard to find for the casual user.

I suggest that the dpctl.tensor API documentation should live at the top-level under API Documentation:

API Documentation |-- dpctl |-- tensor |-- libsyclinterface