Allow adding CommitHooks and EditorProviders dynamically from bundles

Currently, OakSlingRepositoryManager uses a hard-coded list of CommitHook and EditorProvider to be used by the Oak repository. This means that other than building a patched version of OakSlingRepositoryManager there's no way to include a new commit observer. Ideally, a single pseudo-CommitHook and pseudo-EditorProvider should be handled to Oak, and these should just dynamically aggregate all the CommitHook and EditorProvider instances registered in the Whiteboard.

All the currently hardcoded components are already available in the whiteboard, so no functionality will be lost, but this change will automatically enable support for mix:atomicCounter via the AtomicCounterEditorProvider that's not used at the moment.

The old behavior should still be available via a new configuration, OakSlingRepositoryManagerConfiguration#dynamic_components.