[Work items] local board experiment

What does this MR do and why?

Adds an experimental new board feature where boards are generated based on existing work item list data.

This is highly experimental and does not reflect the quality we'd aim for in a finished feature. Raising this MR early to aid in collaboration.

New feature flag will be disabled by default, the the new local-first board will be a dynamic import. So this will not have any impact by default on existing functionality.

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