CPLAT-12469 Update to React 17

[joebingham-wk]

• Updated to React 17
• Removed deprecated APIs that are no longer in use:
  • setReactConfiguration - sourcegraph
  • setReactDOMConfiguration - sourcegraph
  • ReactDartComponentFactoryProxy.reactComponentFactory and ReactDartComponentFactoryProxy2.reactComponentFactory - sourcegraph
  • ReactJsContextComponentFactoryProxy.factory, ReactJsComponentFactoryProxy.factory, and ReactDomComponentFactoryProxy.factory - sourcegraph

QA Instructions

• [ ] verify CI passes
• [ ] verify that over_react CI is passing
• [ ] verify examples work as expected

Please review: @joebingham-wk @aaronlademann-wf @greglittlefield-wf

[joebingham-wk]

@kealjones-wk

[sydneyjodon-wk]

Dart stable is failing from master, but 2.9.2 is passing.