_defineOverlayConfig() {
      const superConfig = super._defineOverlayConfig() || {};
      if (!this.hasArrow) {
        return superConfig;
      }
      return {
        ...superConfig,
        popperConfig: {
          ...this._getPopperArrowConfig(
            /** @type {Partial<PopperOptions>} */ (superConfig.popperConfig),
          ),
        },
      };
    }
Overrides arrow and keepTogether modifier to be enabled,
and adds onCreate and onUpdate hooks to sync from popper state
@configure OverlayMixin
@returns {OverlayConfig}
@protected