Fix: Unfocus YAML Editor on file change

[briangregoryholmes]

The Codemirror editor currently ignores updates that happen while the Editor is focused. This is partly a symptom of our invalidation/refetching approach where an update triggered via keystroke from within the editor is eventually received by the editor again via a prop update. Changing that behavior is an ongoing discussion. Because of that conditional, a focused editor would not update its content even when the underlying file being displayed changed.

This PR adds a key prop to the YAMLEditor that unfocuses the editor whenever the prop changes, allowing the conditional check to pass. Implementing it this way, as opposed to wrapping uses of the component in a key block, ensures the logic is documented/captured with the component.