Add GtkListBox to the a11y tests

testsuite/a11y/listbox.txt

@@ -0,0 +1,115 @@
+window1
+  "window"
+  index: 0
+  state: enabled resizable sensitive showing visible
+  toolkit: gtk
+  <AtkComponent>
+  layer: window
+  alpha: 1
+  box1
+    "list box"
+    parent: window1
+    index: 0
+    state: enabled sensitive showing visible manages-descendants
+    toolkit: gtk
+    <AtkComponent>
+    layer: widget
+    alpha: 1
+    <AtkSelection>
+    selected children: unnamed-GtkContainerAccessible-0
+    unnamed-GtkContainerAccessible-0
+      "panel"
+      parent: box1
+      index: 0
+      state: enabled focusable sensitive showing visible
+      toolkit: gtk
+      <AtkComponent>
+      layer: widget
+      alpha: 1
+      row1
+        "label"
+        parent: unnamed-GtkContainerAccessible-0
+        index: 0
+        name: Row One
+        state: enabled multi-line sensitive showing visible
+        toolkit: gtk
+        <AtkComponent>
+        layer: widget
+        alpha: 1
+        <AtkText>
+        text: Row One
+        character count: 7
+        caret offset: 0
+        default attributes: bg-color: <omitted>
+                            bg-full-height: 0
+                            direction: <omitted>
+                            editable: false
+                            family-name: <omitted>
+                            fg-color: <omitted>
+                            indent: 0
+                            invisible: false
+                            justification: left
+                            language: <omitted>
+                            left-margin: 0
+                            pixels-above-lines: 0
+                            pixels-below-lines: 0
+                            pixels-inside-wrap: 0
+                            right-margin: 0
+                            rise: 0
+                            scale: 1
+                            size: <omitted>
+                            stretch: <omitted>
+                            strikethrough: false
+                            style: <omitted>
+                            underline: none
+                            variant: <omitted>
+                            weight: <omitted>
+                            wrap-mode: word
+    unnamed-GtkContainerAccessible-1
+      "panel"
+      parent: box1
+      index: 1
+      state: enabled focusable sensitive showing visible
+      toolkit: gtk
+      <AtkComponent>
+      layer: widget
+      alpha: 1
+      row2
+        "label"
+        parent: unnamed-GtkContainerAccessible-1
+        index: 0
+        name: Row Two
+        state: enabled multi-line sensitive showing visible
+        toolkit: gtk
+        <AtkComponent>
+        layer: widget
+        alpha: 1
+        <AtkText>
+        text: Row Two
+        character count: 7
+        caret offset: 0
+        default attributes: bg-color: <omitted>
+                            bg-full-height: 0
+                            direction: <omitted>
+                            editable: false
+                            family-name: <omitted>
+                            fg-color: <omitted>
+                            indent: 0
+                            invisible: false
+                            justification: left
+                            language: <omitted>
+                            left-margin: 0
+                            pixels-above-lines: 0
+                            pixels-below-lines: 0
+                            pixels-inside-wrap: 0
+                            right-margin: 0
+                            rise: 0
+                            scale: 1
+                            size: <omitted>
+                            stretch: <omitted>
+                            strikethrough: false
+                            style: <omitted>
+                            underline: none
+                            variant: <omitted>
+                            weight: <omitted>
+                            wrap-mode: word