Support re-writing multiline docstrings into their multiline form

I often wish that people would write something like:

    /** Returns true if the argument should be optional when fully parsed. */
    public static boolean optionalWhenFullyParsed(Argument<?, ?> argument) {
        return argument.isOptional() && argument.defaultValue().isEmpty();
    }

rather than:

    /**
     * Returns true if the argument should be optional when fully parsed.
     */
    public static boolean optionalWhenFullyParsed(Argument<?, ?> argument) {
        return argument.isOptional() && argument.defaultValue().isEmpty();
    }

We could compute whether it would fit on one line and rewrite it if it would. This would only apply to the case of multi-line docstrings that contain a single line. i.e. it would not include:

    /**
     * This is
     * a silly 
     * docstring.
     */
    public static boolean example()

The issue names no files or tests; begin by tracing the formatter entry point that handles Java docstrings. Use the single-line and multiline examples as behavioral cases, preserving multiline docstrings with multiple content lines and rewriting only single-line content that fits on one line.