[FIX] components: avoid leaks when children are outdated/destroyed

Every use case involving some sort of key set on a component would give birth to a leak in an async context:
- If a key of a component changed, the outdated one was never destroyed.
- destroyed component were never removed from their parent's reference map.

This commit solves both issues, that are tightly linked anyway.

src/component/fibers.ts

@@ -144,6 +144,7 @@ export class RootFiber extends Fiber {
 
       // Step 2: patching the dom
       node.bdom!.patch(this.bdom!, Object.keys(node.children).length > 0);
+      node.cleanOutdatedChildren();
       this.appliedToDom = true;
 
       this.locked = false;