Add Plum Lightpad config flow (#36802)

* add support for config flow for Plum Lightpad integration

* add support for config flow for Plum Lightpad integration (remove unintended change to requirements_test_all.txt)

* add support for config flow for Plum Lightpad integration (fix lint issues)

* add support for config flow for Plum Lightpad integration (PR feedback)

* add support for config flow for Plum Lightpad integration (fix lint)

* Update homeassistant/components/plum_lightpad/__init__.py

use debug instead of info for logging

Co-authored-by: Paulus Schoutsen <paulus@home-assistant.io>

* Update homeassistant/components/plum_lightpad/strings.json

switch to use generated references instead of hard-coded strings

Co-authored-by: Paulus Schoutsen <paulus@home-assistant.io>

* Update homeassistant/components/plum_lightpad/strings.json

switch to use references instead of hard-coded string

Co-authored-by: Paulus Schoutsen <paulus@home-assistant.io>

* Update homeassistant/components/plum_lightpad/strings.json

removing translated title per suggestion

Co-authored-by: Paulus Schoutsen <paulus@home-assistant.io>

* Update homeassistant/components/plum_lightpad/strings.json

removing per suggestion

Co-authored-by: Paulus Schoutsen <paulus@home-assistant.io>

* remove unnecessary deepcopy

* remove unnecessary logging warning, since ignoring is expected for configuration.yaml scenario

* switch to hass.loop.create_task per PR feedback

* show login errors when configuring integration via UI (PR feedback)

* disable wrongly flag pylint violation

* add except handler to handle connection errors when setting up config flow entry

* address PR feedback regarding exception handling

* Update homeassistant/components/plum_lightpad/config_flow.py

use helper instead of custom code/message-id

Co-authored-by: Paulus Schoutsen <paulus@home-assistant.io>

Co-authored-by: Paulus Schoutsen <paulus@home-assistant.io>

homeassistant/generated/config_flows.py

@@ -122,6 +122,7 @@ FLOWS = [
     "plaato",
     "plex",
     "plugwise",
+    "plum_lightpad",
     "point",
     "powerwall",
     "ps4",