fixes #19464 - rewrite Dashboard::Manager to support autoloading
Replaces class-level widget storage with a static list of built-in widgets, then appends the registered plugin widgets to get the full default list of widgets. As a result, the class can safely be reloaded when modified and is more testable as class-level state is removed.
Related issues
Refactor #19464: Move Dashboard::Manager out of app/registries/ to permit autoloading
fixes #19464 - rewrite Dashboard::Manager to support autoloading
Replaces class-level widget storage with a static list of built-in
widgets, then appends the registered plugin widgets to get the full
default list of widgets. As a result, the class can safely be reloaded
when modified and is more testable as class-level state is removed.