It previously resided in LibWebView to hide the details of launching a
singleton process. That functionality now lives in LibCore. By moving
this to Ladybird, we will be able to register the process with the task
manager.
It aligns better with the Filesystem Heirarchy Standard[1] to put our
program-specific helper programs that are not intended to be executed by
the user of the application in $prefix/libexec or in whatever the
packager sets as the CMake equivalent. Namely, on Debian systems this
should be /usr/lib/Ladybird or similar.
[1] https://refspecs.linuxfoundation.org/FHS_3.0/fhs-3.0.html#usrlibexec
