Fix react-future warnings and styletron warnings

[twells46]

From reading the docs and visual inspection, styled can be replaced one-to-one with withStyleDeep for composing react-styletron styles.

The router future flags should also require no changes:

• v7_startTransition: We don't use React.lazy so this shouldn't affect us - docs.
• v7_relativeSplatPath: All navigation uses absolute paths (e.g., /tutorials, /scene/jbcSandbox), so this shouldn't affect us - docs.