* Plugins: adds basic PopupExtension point
* Simplify the extension point.
* Excluding the app chrome extension to be rendered on login/signup pages.
* Added feature toggle to be able to disable the app chrome extensions.
* Adding an error boundary around the extension point.
* Changed the way we use the feature toggle.
* moved to use the helper function instead of filtering.
* removed duplace info.
* chore: remove leftover useMemo
---------
Co-authored-by: Marcus Andersson <marcus.andersson@grafana.com>