Make include dir layout consistent with other KF modules
<include visibility layer> / <C++ namespace> / ForwardCamelCase
<include visibility layer> / <C++ namespace lc> / normal class headers
The include visibility layer is named "KFx/Foo", so for the two libs here is "KF6/Plasma" & "KF6/PlasmaQuick". The duplication with the C++ namespace as used with the include subdir is confusing, but by chance in the design.
Tested with find_package(KF6Plasma)
as well as find_package(KF6PlasmaQuick)
, linking the respective libs & includes of #include <plasma_version.h>
, #include <Plasma/Applet>
, #include <PlasmaQuick/Dialog>
.