Add Rainmachine config entry (#18419)

* Initial stuff

* More work in place

* Starting with tests

* Device registry in place

* Hound

* Linting

* Member comments (including extracting device registry)

* Member comments (plus I forgot cleanup!)

* Hound

* More Hound

* Removed old import

* Adding config entry test to coverage

* Updated strings

script/gen_requirements_all.py

@@ -95,6 +95,7 @@ TEST_REQUIREMENTS = (
     'pyunifi',
     'pyupnp-async',
     'pywebpush',
+    'regenmaschine',
     'restrictedpython',
     'rflink',
     'ring_doorbell',