Modernize metadata builder collection factories to Map.of / Set.of

[Copilot]

This updates legacy empty/singleton collection factory usage flagged by modernization checks in the DeltaSpike metadata builder internals. The change is scoped to API modernization only and preserves behavior/runtime constraints.

• Scope

  • Updated only:
    • AnnotatedImpl
    • AnnotationStore

• Collection factory modernization

  • Replaced Collections.singleton(overriddenType) with Set.of(overriddenType).
  • Replaced emptyMap() / emptySet() with Map.of() / Set.of().

• Import cleanup

  • Removed now-unused Collections and static emptyMap / emptySet imports.

// before
typeClosure = Collections.singleton(overriddenType);
annotationMap = emptyMap();
annotationSet = emptySet();

// after
typeClosure = Set.of(overriddenType);
annotationMap = Map.of();
annotationSet = Set.of();