Move ChangesetEvents & Changeset state computation to enterprise
Created by: mrnugget
We should always err on the side of having more code in enterprise than in open.
This moves a lot of the actual code (not type definitions) out of
internal/campaigns/types.go
to multiple files in
enterprise/internal/campaigns
.
This is kinda related to #9101 (closed), because CalcCounts lives in enterprise and sharing code between open and enterprise can get tricky.