Use LatestFedTwo as default federation version

[dotdat]

Makes FederationVersion::LatestFedTwo the default. This is to make sure we are looking forward to the future versions of composition as best as possible.

[dylan-apollo]

I think this would end up being a breaking change for customers, where if they don't have a specific federation version set in their supergraph.yaml, we're suddenly going to start upgrading them to fed 2 mode, right?

[dariuszkuc]

Wondering whether latest is the right default, i.e. we definitely want to update the default to 2.x but I'd argue that we probably would want to target something like latest-1 (or some fixed fed version) for stability purposes.

Since we were defaulting to fed 1, customers wouldn't be using any fed 2 features so technically we could point to just to fed 2.0.