TimePicker: some fixes and polish after testing feedback (#24585)

* make sure we render the delaynow value from dashboard to the time picker settings.

* Added the time zone in the tooltip.

public/app/features/dashboard/components/DashboardSettings/TimePickerSettings.tsx

@@ -133,6 +133,7 @@ export class TimePickerSettings extends PureComponent<Props, State> {
                 invalid={!this.state.isNowDelayValid}
                 placeholder="0m"
                 onChange={this.onNowDelayChange}
+                defaultValue={dashboard.timepicker.nowDelay}
               />
             </Tooltip>
           </div>