Merge WiredTiger changes back to WiredTiger's mainline ("develop") branch. All disagg CI tests pass on merged develop branch, as well as non-disagg CI tests. Regular development now happens in the mainline Github branch and not on a fork. The server's mainline branch picks up new WT disagg code through WT's standard vendoring process.

Merging will include WT disagg support for the small number of WT API changes that have happened since the disagg branch was created.