To speed up Eclipse startup:
EditorRegistry now has distinct map for OS Editors.
Map of OS Editors is only initialized if internal Editor is not found.

Change-Id: I4b61716b7fd9bbed261700f6ab78a412d73b076a
Signed-off-by: Joerg Kubitz <jkubitz-eclipse@gmx.de>
Reviewed-on: https://git.eclipse.org/r/c/platform/eclipse.platform.ui/+/184286
Tested-by: Platform Bot <platform-bot@eclipse.org>
Reviewed-by: Alexander Kurtakov <akurtako@redhat.com>