Add common prefix for compatibility version errors

There is a use case for the compatibility checking code that is part of wiredtiger_open which is more of a query-based mechanism than something used to protect from errors.

On the other hand, having good error messages printed out when compatibility issues are encountered is critical for diagnosability.

With those conflicting requirements, I believe we should prefix all compatibility errors with a common prefix, possibly "Version compatibility detected", and promise not to change that prefix. Once we've done that applications can implement a custom error handler which filters out the compatibility errors when they don't want them to be reported.