Fix memory leak when passing mapped stores as component props

[ealmloff]

Summary

Fixes the unbounded memory growth in #5671.

Store-typed props (Store/ReadStore/WriteStore) get auto_into = true in the props macro, so a mapped store (e.g. an item from store.iter()) passed as a Store<T> prop is converted via From<MappedStore> for WriteStore, which boxes the lens with WriteSignal::new_maybe_sync → CopyValue::new_maybe_sync. Because store types were missing from child_owned_type, that conversion ran in the parent scope's owner: since CopyValue has no Drop, each rerender of the parent leaked one boxed lens per store prop until the parent scope was dropped. In the issue's repro (100 items rerendered on every pointermove), that's ~17 KB leaked per render.

The fix adds looks_like_store_type to child_owned_type, so store prop conversions run inside with_owner(props.owner, …) — the same mechanism already used for ReadSignal/WriteSignal/callback props — and the boxed lens is freed when the props are dropped.

Verified with a counting-allocator harness running the issue's example for 1000 rerenders: heap delta goes from ~17 MB (growing linearly) to flat.

Note: store props still don't participate in the point_to/mark_dirty memoization that signal_fields get in memoize_impl; that's a separate (non-leaking) issue.

Fixes #5671

Link to Devin session: https://dioxus.staging.devinenterprise.com/sessions/671e48ef36ad4dde9bf93eafa654c32c
Requested by: @ealmloff

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