We currently use a combination of our Makefile and the Topologies mtest option to specify what topologies a test should be run against (single, replset, sharded, sharded-replset, load-balanced, serverless).

As it is, when writing a new test we have to "opt-in" to various topologies. It may be cleaner to change the inclusionary Topologies option to an exclusionary ForbiddenTopologies option.

This is worth an investigatory POC, as it's possible this change is larger than it sounds.