[core] Add 'packages' to the config (#5140)

* Initial

* Merge dicts and lists

* feedback

* Move to homeassistant

* feedback

* increase_coverage

* kick_the_hound

homeassistant/bootstrap.py

@@ -395,6 +395,10 @@ def async_from_config_dict(config: Dict[str, Any],
     if not loader.PREPARED:
         yield from hass.loop.run_in_executor(None, loader.prepare, hass)
 
+    # Merge packages
+    conf_util.merge_packages_config(
+        config, core_config.get(conf_util.CONF_PACKAGES, {}))
+
     # Make a copy because we are mutating it.
     # Use OrderedDict in case original one was one.
     # Convert values to dictionaries if they are None