Fix Dom-Reconciliation w/ Headers

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Right now, since columnData.headerRenderer is called directly, React isn't necessarily seeing that the underlying components have changed. This converts the rendering of headers to component syntax to fix errors related to this.

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@benox3 so, interesting thing to discuss here. in order to get this to work, I need to change the type signature of header renderer to be an element, not a node. however, this breaks types if a function were to return a string/number directly. is that a concern here?