Move overviewRuler API under scrollbar

Fixes #5678

typings/xterm.d.ts

@@ -206,12 +206,6 @@ declare module '@xterm/xterm' {
      */
     minimumContrastRatio?: number;
 
-    /**
-     * Controls the visibility and style of the overview ruler which visualizes
-     * decorations underneath the scroll bar.
-     */
-    overviewRuler?: IOverviewRulerOptions;
-
     /**
      * Control various quirks features that are either non-standard or standard
      * in but generally rejected in modern terminals.
@@ -399,8 +393,8 @@ declare module '@xterm/xterm' {
     scrollbarSliderActiveBackground?: string;
     /**
      * The border color of the overview ruler. This visually separates the
-     * terminal from the scroll bar when {@link IOverviewRulerOptions.width} is
-     * set. When this is not set it defaults to black (`#000000`).
+     * terminal from the scroll bar when {@link IScrollbarOptions.width} is set.
+     * When this is not set it defaults to black (`#000000`).
      */
     overviewRulerBorder?: string;
     /** ANSI black (eg. `\x1b[30m`) */
@@ -688,8 +682,8 @@ declare module '@xterm/xterm' {
 
     /**
      * When defined, renders the decoration in the overview ruler to the right
-     * of the terminal. {@link IOverviewRulerOptions.width} must be set in order
-     * to see the overview ruler.
+     * of the terminal. {@link IScrollbarOptions.width} must be set in order to
+     * see the overview ruler.
      * @param color The color of the decoration.
      * @param position The position of the decoration.
      */
@@ -712,16 +706,10 @@ declare module '@xterm/xterm' {
     tooMuchOutput: string;
   }
 
+  /**
+   * Options for configuring the overview ruler rendered beside the scrollbar.
+   */
   export interface IOverviewRulerOptions {
-    /**
-     * When defined, renders decorations in the overview ruler to the right of
-     * the terminal. This must be set in order to see the overview ruler.
-     * This is ignored when {@link IScrollbarOptions.showScrollbar} is false.
-     * @param color The color of the decoration.
-     * @param position The position of the decoration.
-     */
-    width?: number;
-
     /**
      * Whether to show the top border of the overview ruler, which uses the
      * {@link ITheme.overviewRulerBorder} color.
@@ -741,7 +729,7 @@ declare module '@xterm/xterm' {
   export interface IScrollbarOptions {
     /**
      * Whether to show the scrollbar. When false, this supersedes
-     * {@link IOverviewRulerOptions.width}. Defaults to true.
+     * {@link IScrollbarOptions.width}. Defaults to true.
      */
     showScrollbar?: boolean;
     /**
@@ -749,6 +737,18 @@ declare module '@xterm/xterm' {
      * to false.
      */
     showArrows?: boolean;
+
+    /**
+     * The width of the scrollbar and overview ruler in CSS pixels. When set,
+     * this enables the overview ruler.
+     */
+    width?: number;
+
+    /**
+     * Controls the visibility and style of the overview ruler which visualizes
+     * decorations underneath the scroll bar.
+     */
+    overviewRuler?: IOverviewRulerOptions;
   }
 
   /**