Image per step improve preview mode

[shcheklein]

From using it:

https://github.com/iterative/vscode-dvc/assets/3659196/f7b41659-7014-4a56-bcf4-926a63280041

• In the preview screen. As we change the step number we need to also update the preview.
• Multiple previews (?) - need some research
• Ability to lock / unlock step across all / some batches, so that when I update one all others are also updated

That would make way more powerful.