(#7764, 7775, 7778) Revisions to Faces help text

Per UX review of help text, this commit makes several changes over the breadth
of the Faces help:

• Preface API-only action summaries/descriptions with "API only." (issue #7775)
• Provide both CLI and API info in "returns," with the CLI info first. (issue #7778)
• Summaries should be sentences. (Add punctuation.)
• First sentences of descriptions should reiterate summaries. (Summaries and descriptions should be displayed far enough apart that this isn't a problem.)
• Standardize on "subcommand" instead of "face" when talking about the entity you invoke at the command line. (Use "face" when describing API use.)
• Fix outdated or clunky text in several faces.