When investigating WT-11966, I triggered the many collection test on older commits but they no longer build:
https://buildbaron.corp.mongodb.com/ui/#/bf/WT-12230

This is because the test always checkouts the latest mongodb code on that branch and it is no longer compatible with the older WiredTiger commits.

This makes investigating any performance change for that test very hard. We need to find a way to allow us to checkout the compatible mongodb code for the older commits and run the test.