FR: Add credential type to Change/Inject nodes

Ref: https://discourse.nodered.org/t/feature-request-please-add-credential-input-to-inject-and-change-node/95645

Proposal to add the built-in credential type to the appropriate TypedInputs in the Change/Inject nodes. Off the top of my head, I can't think of a technical limitation that would prevent that.

The workaround today is to define an env var at the Flow level as a credential type property, and then reference that in the Change/Inject node. Is that a good enough workaround not to change anything?

Raising here so we don't lose sight of it.