look for xml properties in files with xml file type only
(cherry picked from commit b6ae811) [r=Dmitry.Avdeev]
avoid easy garbage
java.util.ArrayList$Itr: 1,720,417,512 (1%) bytes in 71,684,063 (2%) objects (avg size 24 bytes)
	java.util.ArrayList.iterator: 1,720,392,864 (99%) bytes in 71,683,036 (99%) objects
		com.intellij.openapi.projectRoots.impl.ProjectJdkTableImpl.findJdk: 938,831,640 (54%) bytes in 39,117,985 (54%) objects
		com.intellij.openapi.editor.impl.ComplementaryFontsRegistry.getFontAbleToDisplay: 218,420,520 (12%) bytes in 9,100,855 (12%) objects
(cherry picked from commit 9207b87) [r=Peter.Gromov]
13.0.1
don't generate large substrings when creating CompletionResultSet [r=Peter.Gromov]
"Run in background" option from now on means "show build messages immediately" rather than "execute with modal dialog"