Split EventTargetFactory.in into two files that contain core or modules only event targets.

Auto-generate modules-related event target files and make it ready for moving 
all modules-related files to modules directory.

BUG=371581

Review URL: https://codereview.chromium.org/275283002

git-svn-id: svn://svn.chromium.org/blink/trunk@174218 bbb929c8-8fbe-4397-9dbb-9b2b20218538