Fix/move image to oc namespace

[come-nc]

Summary

Move legacy OC_Image into \OC\Image and update code style and remove deprecated references in there.
This class is exposed through OCP\Image which is used by applications with new \OCP\Image() and then \OCP\IImage methods can be used on it.

This still leaves a reference to OC from OCP which we try to avoid.
But this would mean adding an IImageFactory which applications needs to DI, not sure this is worth it.

Checklist

• Code is properly formatted
• Sign-off message is added to all commits
• Tests (unit, integration, api and/or acceptance) are included
• Screenshots before/after for front-end changes
• Documentation (manuals or wiki) has been updated or is not required
• Backports requested where applicable (ex: critical bugfixes)

[provokateurin]

This broke Talk nextcloud/spreed#13197 and using the OCP replacement does not work.
I think the problem is the \OCP\Image depends on \OC\Image which does not exist in the dependency and thus all methods are missing.
Also some of the methods are only in \OC\Image and not in \OCP\Image or \OCP\IImage and thus are not visible.

To fix this \OCP\Image needs to implement \OCP\IImage directly and the missing method need to be added to \OCP\IImage.