Supporting preview mode at the level of jimage is achieved most efficiently by adding/modifying some flags. Specifically:

1. Flags already present (but unused) in the "/packages/xxx" directory entries can be modified to support preview mode there.
2. New location flags can be added to speed up the pre-processing of preview locations needed for efficient lookup.

This work will bump the minor version (v1.0 -> v1.1) but this is well understood and should be safe.

The only place where a version bump is going to potentially be noticed is if anyone is using the jimage tool from a different JDK to examine new jimage files. This is defined to not work, but the error message can/should be improved to educate anyone caught by it. This will be done in a separate PR.