feat(toolbox): rename label / tooltip getters in ToolboxItem

react/features/base/toolbox/components/AbstractToolboxItem.js

      * provided then it will be translated using it.
      *
      * @protected
-     * @returns {string}
+     * @returns {?string}
      */
-    get _label() {
+    get label(): ?string {
         return this._maybeTranslateAttribute(this.props.label);
     }
 
      * provided then it will be translated using it.
      *
      * @protected
-     * @returns {string}
+     * @returns {?string}
      */
-    get _tooltip() {
+    get tooltip(): ?string {
         return this._maybeTranslateAttribute(this.props.tooltip);
     }
 

react/features/base/toolbox/components/ToolboxItem.web.js

  * Web implementation of {@code AbstractToolboxItem}.
  */
 export default class ToolboxItem extends AbstractToolboxItem<Props> {
-    _label: string;
-    _tooltip: string;
-
     /**
      * Handles rendering of the actual item. If the label is being shown, which
      * is controlled with the `showLabel` prop, the item is rendered for its
             // $FlowFixMe
             <React.Fragment>
                 { this._renderIcon() }
-                { showLabel && this._label }
+                { showLabel && this.label }
             </React.Fragment>
         );
 
             = showLabel ? 'overflow-menu-item-icon' : 'toolbox-icon';
         const iconWrapper
             = React.createElement(elementType, { className }, icon);
-        const tooltip = this._tooltip;
+        const tooltip = this.tooltip;
         const useTooltip = !showLabel && tooltip && tooltip.length > 0;
 
         if (useTooltip) {