Prompt segment configuration snapshots

Problem/Motivation

When editing prompt segment, it would be useful to retain previous version of it, or have multiple 'named' versions of it.

Proposed resolution

There could be configuration snapshots for each segment which would function similar as regular 'revisions' from user perspective.

That would also be better alternative to #3384408: Fully implement revisions, because:

• granular per each segment
• would have fine-tuned user interface
• would work with configuration entities as well

Remaining tasks

User interface changes

API changes

Data model changes