Feature: #78695 - Set the session timeout for frontend users

See forge#78695


Previously it was possible to set the lifetime of a frontend user session via cookie, which validated the session on the client-side, for the server-side there was only an option for backend user sessions.

Setting the option $GLOBALS['TYPO3_CONF_VARS']['FE']['sessionTimeout'] is now possible (via the Install Tool) to configure a global timeout for frontend sessions on the server-side.