Inherit parent's app ID when creating a new cgroup for tabs

When creating a cgroup for a tab, we would use a hardcoded string as
cgroup name that included `org.kde.konsole` as app ID. This leads to
tabs incorrectly being attributed to Konsole in System Monitor's
application page, even if the tab is actually embedded in a different
application such as Kate.

Instead of hardcoding the app ID, use the application's desktop file
name, so that if we lookup the app ID from a cgroup name, we get back to
the original application instead of Konsole.

BUG: 508716

src/ProcessInfo.cpp

@@ -11,6 +11,7 @@
 #include "NullProcessInfo.h"
 #include "ProcessInfo.h"
 #include "UnixProcessInfo.h"
+#include "konsoledebug.h"
 
 // Unix
 #ifndef Q_OS_WIN
@@ -26,6 +27,7 @@
 // Qt
 #include <QDir>
 #include <QFileInfo>
+#include <QGuiApplication>
 #include <QHostInfo>
 #include <QStringList>
 #include <QTextStream>
@@ -624,7 +626,6 @@ private:
         const pid_t selfPid = getpid();
 
         const QString managerObjPath(QStringLiteral("/org/freedesktop/systemd1"));
-        const QString appUnitName(QStringLiteral("app-org.kde.konsole-%1.scope").arg(selfPid));
 
         // check if systemd dbus services exist
         if (!QDBusConnection::sessionBus().interface()->isServiceRegistered(QStringLiteral("org.freedesktop.systemd1"))) {
@@ -634,6 +635,9 @@ private:
         // get current application cgroup path
         const QString oldAppCGroupPath(getProcCGroup(selfPid));
 
+        auto appUnitName = QStringLiteral("app-%1-%2.scope").arg(QGuiApplication::desktopFileName()).arg(selfPid);
+        qCDebug(KonsoleDebug) << "Creating scope" << appUnitName;
+
         // create application unit
         VariantList properties;
         const QList<uint> mainPid({static_cast<quint32>(selfPid)});