Block Editor: URLInput: Soft-deprecate label prop

[aduth]

Previously: #18061 (comment)

As discussed in #18061, the new LinkControl component can be considered as a composite component of URLInput, plus labeling behaviors associated with similar *Control input control components.

Diagram (not including label):

In this model, URLInput should be considered a very barebones component whose sole responsibility should be to render an input field and associated URL autocompletion results from which to pick a value.

This component would not accept a label prop. However, since URLInput already does accept label, we should soft-deprecate it in the following manner:

• Continue to accept label
• If label is provided:
  • Log a deprecated message
  • Render <LinkControl /> with the given label and relevant props
    • LinkControl will recursively render URLInput, but it should not pass label, thus avoiding recursion