Performance Improvements

[NateLanza]

Does this PR close any open issues?

Closes #334

Give a longer description of what this PR addresses and why it's needed

Improves performance across a variety of actions by reducing unnecessary re-renders. Includes:

• Adding WhyDidYouRender plugin to dev mode for debugging re-renders
• Wrapping the VegaLite element in the attribute density plots with a memoized component that only depends on strictly necessary props
• Preventing unnecessary re-renders during sorting, aggregation, hovering, selection, and visible attribute changes
• Using Recoil state in App to memoize rows
• Replacing VERY costly getValuesFromRow function in AttributeBar with a memoized Recoil selector
• Memoizing props fed to VegaLite component in element view sidebar
• Not rendering ElementSidebar component unless it is open

Provide pictures/videos of the behavior before and after these changes (optional)

No visible changes to behavior other than speedup

Have you added or updated relevant tests?

• Yes
• No changes are needed

Have you added or updated relevant documentation?

• Yes
• No changes are needed

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[JakeWags]

Looks great. A few changes for clarity, but not blocks to merging.