Have all krunner plugin desktop files prefixed with "plasma-runner-"

Summary:
With all desktop files being installed in KDE_INSTALL_KSERVICES5DIR,
having a namespace prevents clashes and also helps identifying the files.

Reviewers: #plasma, broulik, apol

Reviewed By: apol

Subscribers: plasma-devel

Tags: #plasma

Differential Revision: https://phabricator.kde.org/D10515

runners/appstream/CMakeLists.txt

@@ -4,4 +4,4 @@ add_library(appstreamrunner MODULE appstreamrunner.cpp)
 target_link_libraries(appstreamrunner PUBLIC KF5::Runner KF5::I18n KF5::Service AppStreamQt)
 
 install(TARGETS appstreamrunner DESTINATION ${PLUGIN_INSTALL_DIR})
-install(FILES appstreamrunner.desktop DESTINATION ${SERVICES_INSTALL_DIR})
+install(FILES plasma-runner-appstream.desktop DESTINATION ${SERVICES_INSTALL_DIR})

runners/recentdocuments/CMakeLists.txt

@@ -15,4 +15,4 @@ target_link_libraries(krunner_recentdocuments
 
 install(TARGETS krunner_recentdocuments DESTINATION ${KDE_INSTALL_PLUGINDIR} )
 
-install(FILES recentdocuments.desktop DESTINATION ${KDE_INSTALL_KSERVICES5DIR})
+install(FILES plasma-runner-recentdocuments.desktop DESTINATION ${KDE_INSTALL_KSERVICES5DIR})