* Add the $wgExtendedLoginCookies configuration variable, which defines
the set of login cookies that can have their lifetime configured
independently
* Add the $wgExtendedLoginCookieExpiration configuration variable, which
dictates when the extended lifetime login cookies expire
* Default $wgExtendedLoginCookieExpiration to null so that the current
behaviour is unaffected
Bug: T68699
Change-Id: I0cc24524e4d7d9d1d21c9fa8a28c7c76b677b96c
