* feat(extensions): don't allow core grafana extension point ids in plugins
* feat(extensions): log more specific errors if extension point id validation fails
* chore: move the ExtensionSidebar ext. point id to grafana-data
* review: remove type assertion
* feat: add generic plugin extension functions
* updated betterer.
* Fixed type issues after sync with main.
* Remved extensions from datasource and panel.
* Added validation for extension function registry.
* Added tests and validation logic for function extensions registry.
* removed prop already existing on base.
* fixed lint error.
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Co-authored-by: Marcus Andersson <marcus.andersson@grafana.com>