[PATCH] QML engine: Correctly compare composites when multiple engines are used

[PATCH] QML engine: Correctly compare composites when multiple engines are used

Since 6.11, we allow multiple types to be active for the same URL.
While we converted multiple places to handle this, we missed adjusting
the property validator. There, we just picked the last inserted property
cache, which can lead to validation failures.

Fix this by adding a fallback path which checks all potential matches
when the initial lookup would yield an error.

The same kind of check is also needed in qmlobject_can_qml_cast.

Amends 9cc23ca91c404f24fff3c36e8c9425ae674f341d.

Change compared to 6.12:
Dropped the isComposite check, which doesn't exist there. That causes
one potential extra unneeded lock acquisition, but only in a case
where'd we get an error anyway.

Fixes: QTBUG-149607
Change-Id: Ibd0df2325807e75b23056ebc0bacdfe877b002f3
Reviewed-by: Ulf Hermann <ulf.hermann@qt.io>
(cherry picked from commit 94a76ed58629932f6d689c48ecf8d3132188923b)
Reviewed-by: Qt Cherry-pick Bot <cherrypick_bot@qt-project.org>
(cherry picked from commit 8c23f65ec4889f9ff7f609002a129698796de2b8)

Gbp-Pq: Name upstream_2efb7c6_correctly_compare_composites_with_multiple_engines.diff