This was used to get around the KProcess class being incomplete. We can
just move this to the cpp file and eliminate the cast entirely, letting
the compiler do its work.
This formats all copyright comments according to SPDX formatting guidelines.
Additionally, this resolves the remaining GPLv2 only licensed files by relicensing them to GPLv2.0-or-later.
This allows for better compiler errors, where the compiler will state a
copy or move couldn't occur due to the relevant function being deleted.
Previously a compiler would warn about the relevant function not being
accessible (which, while true, isn't as informative as it could be).