Allow to query annotations as metrics. Switch annotation implementation to React

[fetzerch]

• Events / annotations can now be queried as metrics. This allows to visualize for example today's sunrise/sunset time on dashboards.
  • To show e.g. the sunrise timestamp:
  • Add a SingleStat visualization
  • Add 'Sunrise' as query
  • Select 'Time' as 'Field'
  • In 'Unit' enter 'time: HH:mm' to show only the hour and the minute.
  • It also works with multiple events:
  • Add a singlestat visualization
  • Add 'Sunrise' and 'Sunset'
  • Add a 'Rename by regex' transformation: 'Match': time, 'Replace': '${__series.name}'
  • In 'Fields' select '${__series.name}' (if you only select 'Time' it will just show 'No Value')
  • In 'Unit' enter 'time: HH:mm' to show only the hour and the minute.
• Fixed: Noon and Midnight notification did not show correct values for non default timezones.
• Added: A single query now supports multiple metrics.

This change should help to keep the plugin compatible with the upcoming Grafana v10 that will no longer support the old Angular based annotations.

Fixes #20 Closes #48

TODO:

• [x] Add new screenshots
• [x] Add new version of dashboard to dev-env
• [x] Add new version of dashboard to grafana
• [x] Automatically suggest units

[fetzerch]

@ecraven It would be nice if you could test this implementation because it supersedes your Pull Request. It would also nice if you could share the JSON for your dashboard. Especially the Moon visualization looks quite interesting!