FED-3282 Suppress react_dom render warnings

[greglittlefield-wf]

Motivation

In React 18, each react_dom.render call emits the following console.error message:

Warning: ReactDOM.render is no longer supported in React 18. Use createRoot instead. Until you switch to the new API, your app will behave as if it's running React 17. Learn more: https://reactjs.org/link/switch-to-createroot

Since we likely won't be adding support for createRoot until after we've switched to React 18, consumers won't be able to address these errors, and they'd be quite noisy in the meantime.

Solution

• Suppress console.error messages warning about ReactDOM.render's deprecation
• Add regression test
• Remove / repurpose old console.warn wrapping for similar message suppression, which isn't needed in Dart 2.14+
  • Up SDK constraint to 2.14 (could probably be higher, but that's out of scope)
  • Remove old "legacy" test configs

Testing instructions

• CI passes
• Regression test, added in 52f1a56, fails before the fix was added

[sydneyjodon-wk]

+10 🎉

• CI passes
• Regression test, added in 52f1a56, fails before the fix was added

[greglittlefield-wf]

@Workiva/release-management-p

[rmconsole-wf]

+1 from RM