more clearly list Android enum values docs in JavaDoc

[incanus]

Tail work from #6508 referenced in #6508 (comment).

We want better cross-linking between symbols in the JavaDoc. An example:

    //ICON_ROTATION_ALIGNMENT: In combination with `symbol-placement`, determines the rotation behavior of icons.

    /**
     * When `symbol-placement` is set to `point`, aligns icons east-west. When `symbol-placement` is set to `line`, aligns icon x-axes with the line.
     */
    public static final String ICON_ROTATION_ALIGNMENT_MAP = "map";
    /**
     * Produces icons whose x-axes are aligned with the x-axis of the viewport, regardless of the value of `symbol-placement`.
     */
    public static final String ICON_ROTATION_ALIGNMENT_VIEWPORT = "viewport";
    /**
     * When `symbol-placement` is set to `point`, this is equivalent to `viewport`. When `symbol-placement` is set to `line`, this is equivalent to `map`.
     */
    public static final String ICON_ROTATION_ALIGNMENT_AUTO = "auto";

    @StringDef({
            ICON_ROTATION_ALIGNMENT_MAP,
            ICON_ROTATION_ALIGNMENT_VIEWPORT,
            ICON_ROTATION_ALIGNMENT_AUTO,
        })
    @Retention(RetentionPolicy.SOURCE)
    public @interface ICON_ROTATION_ALIGNMENT {}

Here, symbol-placement should be symbolPlacement and should @link properly. Also, point should be SYMBOL_PLACEMENT_POINT, line should be SYMBOL_PLACEMENT_LINE, and viewport should self-identify and be ICON_ROTATION_ALIGNMENT_VIEWPORT.

We already do this on Darwin (as of #6508) but considering Android was ready to go even without spec enum documentation, this can be release tail work and #6508 gets us an improvement on the books.

/cc @ivovandongen @zugaldia @1ec5