Packages feature (#1052)

* Started to work on packages feature

* Added some more validation to packages config

* Fixed some linter warnings

* Updated tests

* Reordered consts to avoid linter error

* Reordered consts to avoid linter error

* Refactored test yaml files to integrate into existing test pipeline

Co-authored-by: Dmitry Berezovsky <dmitry.berezovsky@logicify.com>

tests/test_packages/test_uptime_sensor.yaml

@@ -0,0 +1,5 @@
+# Uptime sensor.
+platform: uptime
+id: ${devicename}_uptime_pcg
+name: Uptime From Package
+update_interval: 5min