spike: data-items nested change detection

[jfmcquade]

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Description

WIP solution to #2636.

When rendering row.rows in the data-items component template, the value of the nested row does update dynamically when the local variable changes. But this change is not reflected in the value rendered in the title component.

debug_data_items_local:

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[chrismclarke]

Thanks for creating the debug sheet and initial investigation. I came to the same conclusion as you, that actually everything looks correct from the populated data but for some reason the nested template isn't recompiling as expected.

I've tried to track down the cause and apply a fix in #2639