This process includes:
- Adding FCV 4.2.
- Removing FCV 3.6.
- Setting FCV 4.0 to be the default value of the FCV parameter for new shard servers.
- Updating "latest" FCV to be 4.2 and "last-stable" FCV to be 4.0.
- Changing generic references to refer to the latest upgraded and downgraded versions.