Add Jellyfin integration (#44401)

* Initial commit after scaffold setup

* Add initial config flow

* Create initial entity

* Ready for testing

* Can browse, no result yet

* Further improvements. Browsing is working.
Now need to work on proper stream URL

* Two valid URLs. Do not play in HA

* First working version for music

* Add thumbnail

* Includes Artist->Album hierarchy

* Add sorting of artists, albums and tracks

* Remove code for video libraries

* Improved code styling

* Optimize configuration flow

* Fix unit tests for config flow

* Fix import order

* Conform to style requirements

* Use empty string as media type for non playables

* 100% code coverage config_flow

* Type async_get_media_source

* Final docsctring fix after rebase

* Add __init__ and media_source files to .coveragerc

* Fix testing issues after rebase

* Fix string format issues and relative const import

* Remove unused manifest entries

* Raise ConfigEntry exceptions, not log errors

* Upgrade dependency to avoid WARNING on startup

* Change to builtin tuple and list (deprecation)

* Log broad exceptions

* Add strict typing

* Further type fixes after rebase

* Retry when cannot connect, otherwise fail setup

* Remove unused CONFIG_SCHEMA

* Enable strict typing checks

* FlowResultDict -> FlowResult

* Code quality improvements

* Resolve mypy.ini merge conflict

* Use unique userid generated by Jellyfin

* Update homeassistant/components/jellyfin/config_flow.py

Remove connection class from config flow

Co-authored-by: Milan Meulemans <milan.meulemans@live.be>

* Minor changes for additional checks after rebase

* Remove title from string and translations

* Changes wrt review

* Fixes based on rebase and review suggestions

* Move client initialization to separate file

* Remove persistent_notification, add test const.py

Co-authored-by: Milan Meulemans <milan.meulemans@live.be>