Fix TensorFlow docs cannonical name chooser

Prefer `tf.submodule.thing` to `tf.thing` as the canonical doc location.

For class members, prefer the defining class.

Always prefer the non-contrib version.

Choose the shortest name, but prefer sub-modules.
(1.10 is includes submodules like tf.io and tf.math)

PiperOrigin-RevId: 207756817