* Remove `:type` lines now sphinx-autoapi supports typehints

Since we have no updated sphinx-autoapi to a more recent version it
supports showing type hints in the documentation, so we don't need to
have the type hints _and_ the `:type` lines -- which is good, as the
ones in the doc strings are easy to get out of date!

The following settings have been set:

`autodoc_typehints = 'description'` -- show types in description (where
previous `:type` used to show up)

`autodoc_typehints_description_target = 'documented'` -- only link to
types that are documented. (Without this we have some missing return
types that aren't documented, and aren't linked to in our current python
API docs, so this caused a build failure)

`autodoc_typehints_format = 'short'` -- Shorten type hints where
possible, i.e. `StringIO` instead of `io.StringIO`

* Add argument type names to local spelling dictionary

Now that we are using the type hints in the docs, sphinxcontrib-spelling
picks them up as words to be checked, so we have to ignore them.

I've chosen to add the provider specific ones to local dictionary files
rather than the global, as for example, `mgmt` is an error in most
places, but not in some of the Azure provider.