Rework descriptor mechanism

Currently there are several issues with the descriptor mechanism, and several needed improvements :

• using a generic interface to be implemented is a big constraint on "freely annotated xmap" classes, maybe using an annotation instead would be good
• the merge/override logics needs to be handled in a way that leads developers towards a "standard" way, but still including historic use cases to allow migration to the new system (still, using annotations)
• lazy merge/override done on this registry requires caches logics: it would be better not to have a lazy behaviour, and compute it once, at framework startup
• (detail, maybe related) not sure why DefaultComponent holds the descriptor as a class field right now: a lookup, when needed, should be enough
• when retrieving descriptors from this generic registry, it is not possible anymore to know the contributing component, which does not allow proper error management (NXP-29573, NXP-28948)
• ideally, all default platform components should be migrated to use this registry, to encourage moving to this new system

Related improvements

• a global registry handling all resources allows more easily to document and track overrides on contributions (and order can be documented, see NXP-29569 and NXP-29022 on explorer side)
• similarly to merge/override, handle contribution enablement in a standard way
• all components that can handle hot-reload would be covered generically

Pros

• runtime services behaviour would be more homogeneous, less error-prone, more user friendly for people writing new components, and people contributing to them
• it would be easier for Studio to contribute to any extension point, with hotreload covered by the target service
• the declarative approach using annotations makes it easier to understand and document the service merge/override behaviours, and encourages one "default" approach for new components
• later, this would also ease up migration towards a better system than xmap for processing of services/contributions (typically spring)