Use tab in shortcut to switch tabs
In #7218 (closed), we used arrow to avoid collision in browser. But later we has to modify some <Ctrl> shortcut for <Alt> version any way.
Also as https://discuss.tryton.org/t/key-shortcuts-in-text/1099 shows <Ctrl>left / <Ctrl>right are used to navigate inside an entry.
So I think it is better to use <Ctrl>tab and <Alt>tab.