Refactor nzbget to support future platform changes

[chriscla]

Breaking Change:

The NZBGet integration has been changed to support multiple platforms and future events, and common code has been centralized to the component. The configuration has moved from the sensor platform to the nzbget key in configuration.yaml, and the monitored_variables option has been removed. Users need to update their configuration.

Description:

Re-factor NZBGet component to move core logic out of the sensor platform and into a common component. Update config to have a nzbget: root-level entry.

Pull request with documentation for home-assistant.io (if applicable): home-assistant/home-assistant.io/pull/10300

Example entry for configuration.yaml:

nzbget:
  host: 192.168.1.1
  ssl: false  

Checklist:

• The code change is tested and works locally.
• Local tests pass with tox. Your PR cannot be merged unless tests pass
• There is no commented out code in this PR.
• I have followed the development checklist

If user exposed functionality or configuration variables are added/changed:

• Documentation added/updated in home-assistant.io

If the code communicates with devices, web services, or third-party tools:

• The manifest file has all fields filled out correctly. Update and include derived files by running python3 -m script.hassfest.
• New or updated dependencies have been added to requirements_all.txt by running python3 -m script.gen_requirements_all.
• Untested files have been added to .coveragerc.

[MartinHjelmare]

We shouldn't make any changes to this integration until a pypi library is used for the api interface.

[MartinHjelmare]

Nice!

[MartinHjelmare]

Great! Just a small comment.

[MartinHjelmare]

Please solve the merge conflict.

[chriscla]

@MartinHjelmare -- thank you for all the review comments and support :) It's really appreciated as someone new here.

I'm making the config change so that I can add more to the component (e.g. stop nzbget service, event when a download completes, etc...). Right now though, this change just has the sensor platform. So it's a breaking change without additional functionality. Should I go forward with this change or should I re-factor it so it's non-breaking and then do the break when I add more features? I would prefer to go forward with this and just add the new functionality asap.

Also, the CI (Overview Validate) keeps failing asking me to run the requirements script. I've done that on an updated rep, so I'm not sure what's going on.

[MartinHjelmare]

I think we can move forward with this PR as a breaking change.

Please run python3 -m script.hassfest to update codeowners file.

[MartinHjelmare]

Great!