[release/21.08] Make Konqueror compatible with KIO 5.86.0
Due to a change in KIO::DesktopExecParser::hasSchemeHandler (commit 5fa55a2395cbfb6504e56bf71c869c8e49902e13Q) URLs entered in the navigation bar either were always opened in a new tab or they were opened in another program altogether (for example, man and info URLs).
To fix this issue, it has been necessary to copy the implementation of KRun::init and KParts::BrowserRun::init in KonqRun::init, making the necessary changes to restore the old behaviour.
BUG: 442636 (cherry picked from commit ba1ea2b7)