fix: await in each block over store re-runs infinitely

[hmnd]

fixes #17471, fixes #17394

This was happening because mutable_source uses safe_equals which always treats objects as different, so the async derived within would always be marked as dirty and re-run.

My fix tracks object refs between async derived runs, and skips re-running if they haven't changed. I've included two test samples, as my first pass at this didn't check if we were in the same batch, which broke updating a prop on an object with an unchanged ref. I haven't been able to get the first sample with each to fail because it freezes the test runner instead :) not sure how best to handle that without introducing a timeout feature to the runner.

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