fix: Update anyOf schema to correctly update items in an array

[SuriGill]

Reasons for making this change

componentWillReceiveProps is no longer recommended by React after updating to React 16 as it has some design flaws. Instead, I've updated to a componentDidUpdate that will change after formData changes specifically. I've added a test to demonstrate the bug that was causing an update twice and selectedOption to become out of sync when moving indices in an array using anyOf.

If this is related to existing tickets, include links to them as well.

fixes first issue in #1486

Checklist

• I'm updating documentation
  • I've checked the rendering of the Markdown text I've added
• I'm adding or updating code
  • I've added and/or updated tests
  • I've updated docs if needed
• I'm adding a new feature
  • I've updated the playground with an example use of the feature

[epicfaace]

Thanks! Might it have been better to use getDerivedStateFromProps instead though? I won't block merging the PR on this, though, as this is clearly an improvement from the previous code.

[epicfaace]

Why did you add the !prevState check @SuriGill ? It seems like the tests already pass without it.