dataengines/executable: confirm before running commands

The dataengine can't just let a widget run arbitrary commands.

A new environment variable "PLASMA_DATAENGINE_DISABLE_COMMANDS" is added to disable the dataengine for convenience.

confirmation

List of QML files which call PlasmaCore.DataEngine with engine=executable:

./1961015/tw.ltlnx.textviewerwidget/contents/ui/main.qml
./1952906/org.kde.plasma.ecowatt/contents/ui/main.qml
./1945081/org.kde.batteryBar/contents/ui/config/SourceSettings.qml
./1945081/org.kde.batteryBar/contents/ui/Battery.qml
./1935442/com.kainat.binarylayoutsaver/contents/ui/FullRepresentation.qml
./1934103/contents/ui/main.qml
./1932321/TiledScreen/contents/ui/lib/AppletVersion.qml
./1927520/onedrive-applet/package/contents/ui/FullRepresentation.qml
./1909220/contents/ui/main.qml
./1884528/ydinfo-0.0.7/contents/ui/main.qml
./1878511/contents/ui/main.qml
./1878384/contents/ui/main.qml
./1852610/package/contents/ui/main.qml
./1833519/contents/ui/main.qml
./1833519/contents/ui/ConfigGeneral.qml
./1833220/SimpleOverviewPager/contents/ui/main.qml
./1830364/org.kde.plasma.weblabel/contents/ui/main.qml
./1829436/contents/ui/components/Exec.qml
./1829274/contents/ui/main.qml
./1804745/contents/ui/config.qml
./1804745/contents/ui/main.qml
./1787425/org.kde.plasma.ksys76power/contents/ui/main.qml
./1741497/org.kde.plasma.stufffix/contents/ui/main.qml
./1735447/org.kde.willow-light.desktop/contents/splash/Splash.qml
./1735447/org.kde.willow-light.desktop/contents/lockscreen/willowComponents/PowerMenu.qml
./1719511/com.github.doncsugar.presentwindows/contents/ui/Main.qml
./1719511/com.github.doncsugar.presentwindows/contents/ui/lib/ExecUtil.qml
./1719511/com.github.doncsugar.presentwindows/contents/ui/lib/AppletVersion.qml
./1704465/adhe.textcommand/contents/ui/main.qml
./1691743/com.github.varlesh.greybird-darker/contents/lockscreen/LockScreenUi.qml
./1689651/contents/ui/Exec.qml
./1689651/contents/ui/NordVPN.qml
./1663528/com.github.varlesh.nova-Papilio/contents/lockscreen/LockScreenUi.qml
./1662817/com.github.varlesh.nova-Pengi/contents/lockscreen/LockScreenUi.qml
./1661587/com.github.varlesh.nova-Leo/contents/lockscreen/LockScreenUi.qml
./1660775/com.github.varlesh.nova-Amare/contents/lockscreen/LockScreenUi.qml
./1659904/com.github.varlesh.nova-Lacus/contents/lockscreen/LockScreenUi.qml
./1660082/org.kde.plasma.kompressor/contents/ui/main.qml
./1659134/com.github.varlesh.nova-Terra/contents/lockscreen/LockScreenUi.qml
./1596560/plasmoid/contents/ui/FullRepresentation.qml
./1596521/contents/ui/main.qml
./1584342/contents/ui/SessionControlBar.qml
./1575231/org.kde.plasma.msirgb/contents/ui/main.qml
./1574941/org.kde.plasma.tomatoid5/contents/ui/main.qml
./1544959/Menu11-main/contents/ui/Footer.qml
./1528901/contents/ui/main.qml
./1527636/contents/ui/components/NetworkInterfaceDetector.qml
./1526282/org.kde.plasma.ipinfo/contents/ui/main.qml
./1521795/com.github.varlesh.greybird/contents/lockscreen/LockScreenUi.qml
./1519916/kxn.menus.corner/contents/ui/main.qml
./1509103/contents/ui/main.qml
./1502826/contents/code/main.qml
./1495813/org.kde.plasma.kickoff/contents/ui/Kickoff.qml
./1494502/contents/ui/main.qml
./1493231/org.kde.plasma.taskmanager/contents/ui/ConfigBehavior.qml
./1483671/contents/ui/main.qml
./1479178/contents/ui/main.qml
./1475528/plugin/contents/ui/Pyext.qml
./1462622/com.github.varlesh.materia/contents/lockscreen/LockScreenUi.qml
./1462614/com.github.varlesh.materia-light/contents/lockscreen/LockScreenUi.qml
./1455101/contents/ui/main.qml
./1431550/package/contents/ui/config/configGeneral.qml
./1431550/package/contents/ui/main.qml
./1425330/org.kde.plasma.videocard/contents/ui/main.qml
./1426768/contents/ui/main.qml
./1420222/org.kde.plasma.mailnag/contents/ui/main.qml
./1415012/org.kde.offMonitor/contents/ui/CompactRepresentation.qml
./1411472/org.kde.plasma.prostatus/contents/ui/main.qml
./1408433/org.kde.thermalMonitorFix/contents/ui/config/ConfigTemperatures.qml
./1408433/org.kde.thermalMonitorFix/contents/ui/main.qml
./1402942/org.kde.plasma.bigSur-inlineBattery/contents/ui/lib/AppletVersion.qml
./1395666/org.kde.plasma.translator/contents/ui/config/configGeneral.qml
./1395666/org.kde.plasma.translator/contents/ui/main.qml
./1387238/com.github.adhec.DynamicTheme/contents/ui/main.qml
./1387238/com.github.adhec.DynamicTheme/contents/ui/ConfigGeneral.qml
./1386465/AvalonMenu/contents/ui/MenuRepresentation.qml
./1384156/org.kpple.kppleMenu/contents/ui/main.qml
./1384066/contents/ui/main.qml
./1383271/com.github.adhec.SwitchTheme/contents/ui/ConfigGeneral.qml
./1383271/com.github.adhec.SwitchTheme/contents/ui/FullRepresentation.qml
./1381655/contents/ui/lib/AppletVersion.qml
./1371502/contents/ui/newEmail.qml
./1369390/org.kde.drydock/contents/ui/main.qml
./1367178/menuX/contents/ui/SideBarItem.qml
./1367167/menuZ/contents/ui/CompactRepresentation.qml
./1365044/applet-latte-sidebar-button-0.1.2/contents/ui/main.qml
./1364107/contents/ui/main.qml
./1364071/SimplePager/contents/ui/main.qml
./1349610/ru.konstantinz.snowfall/contents/ui/main.qml
./1348495/contents/ui/config/ConfigFanspeeds.qml
./1348495/contents/ui/main.qml
./1349326/m4qu3l4n.desktop.penguin/contents/ui/main.qml
./1336269/contents/ui/main.qml
./1335518/kde-plugin/contents/ui/MakeThatPape.qml
./1326546/plasmoid/contents/ui/config/ConfigBackend.qml
./1326546/plasmoid/contents/ui/config/ConfigEffect.qml
./1326546/plasmoid/contents/ui/WsConnection.qml
./1326546/plasmoid/contents/ui/ShaderSource.qml
./1325685/contents/ui/main.qml
./1324206/org.kde.plasma.navdexie/contents/ui/CompactRepresentation.qml
./1319588/contents/ui/Main.qml
./1319588/contents/ui/lib/AppletVersion.qml
./1313987/org.kde.plasma.advancedradio/contents/ui/config/configGeneral.qml