Update documentation structure and start migrating to markdown (#934)

Starts structuring the documentation library usage into Tutorials, Guides, Explanations and Reference.
Continues migrating new docs from rst to markdown.
Extends the test framework discovery mocks to allow easy writing and testing of code examples.

docs/source/deprecated.md

@@ -0,0 +1,24 @@
+# Deprecated API
+
+```{currentmodule} kasa
+```
+The page contains the documentation for the deprecated library API that only works with the older kasa devices.
+
+If you want to continue to use the old API for older devices,
+you can use the classes in the `iot` module to avoid deprecation warnings.
+
+```py
+from kasa.iot import IotDevice, IotBulb, IotPlug, IotDimmer, IotStrip, IotLightStrip
+```
+
+
+```{toctree}
+:maxdepth: 2
+
+smartdevice
+smartbulb
+smartplug
+smartdimmer
+smartstrip
+smartlightstrip
+```