Motivating PR comment here.

This ticket is to think about future proofing live restore in case we make breaking changes in future, such as adding or removing new states. An important case to consider is if we could start live restore using "version 1" but then continue the restore at a later date with code implementing "version 2".

We've seen cases like this before, for example the logging system is now up to version WT_LOG_V5_VERSION so we can use that as a point of reference.