Deprecate the AbstractDeclarativeScopeProvider class #3628
Description
The usage of the org.eclipse.xtext.scoping.impl.AbstractDeclarativeScopeProvider class is discouraged, as stated out by @szarnekow in the EclipseCon France talk in 2017.
That's why the AbstractDeclarativeScopeProvider class should be deprecated in favor of the org.eclipse.xtext.scoping.impl.DelegatingScopeProvider class to encourage the users still using the "old way" to reimplement their scope provider.
That would bring the following benefits to the clients:
- It will be easier to debug, easier to understand, and depending on the language, it may gain performance improvements.
- Moreover it will also fix SonarQube issues in the custom ScopeProvider class: "Rename this method name to match the regular expression '^[a-z][a-zA-Z0-9]*, since the scoping methods do not need will not contain _ anymore.