Add "Force New Tabs" option

Adds a new "Force New Tabs" option in Konsole, which essentially is like if you passed --new-tab for each konsole invocation.

This is useful when you don't want to implement workarounds to make Konsole open in new tabs on every application that you use. To me, this is useful to override Dolphin's default "Open Terminal Here" behavior.

Here's a thread on KDE Discuss of users trying to make Konsole always open in a new tab, which essentially boils down to "override the .desktop file but even then not every app may respect this decision": https://discuss.kde.org/t/how-could-i-reroute-every-konsole-opening-intent-to-open-a-tab-instead/7008

There are two caveats with this change however:

• When opening a new tab, the Konsole window is not automatically put in focus. However I don't know if this in the scope of this PR because this is the current Konsole behavior if you use --new-tab.
• The new option does require Konsole's "Use the same process for every window" because, if it is not enabled, it won't work, just like how --new-tab works. Maybe the option should be disabled/grayed out if the option is not enabled?

This is my first PR and the first time I've used C++ and Qt, so if there is anything that must be changed, please let me know! Because I've probably done some dumb things in the code. 😄

(build is failing but master is also failing with the same error)