Comprehensive docstring cleanup across the repository — fix Sphinx
cross-references, Python REPL continuation syntax, stale class names,
and modernize the IotBulb docstring to use the
`Module.Light`/`Module.LightPreset` interface.
Adds light preset common module for switching to presets and saving presets.
Deprecates the `presets` attribute and `save_preset` method from the `bulb`
interface in favour of the modular approach. Allows setting preset for `iot`
which was not previously supported.
