Missing @ExtensionPoint implementations in core Druid

When a method has a default empty implementation in an `@ExtensionPoint` interface for backwards compatibility with extensions, we need to ensure somehow that implementations in the main Druid tree don't omit that methods themselves, or we have problems like #6893.

Alternatively the default implementations could be just removed, so we break extensions. I think it's OK in minor Druid versions (e. g. 0.13 -> 0.14)

Start by tracing the @ExtensionPoint interfaces and their default empty methods, then inspect implementations in the main Druid tree and review issue #6893 for the failure being prevented. Define whether the intended outcome is an enforcement mechanism or removal of defaults; done means core implementations cannot silently omit these methods while the compatibility decision is documented.

Written by the indexing model from the issue text.