Fixes missing target types in `TargetTypeEnum` and separates the
EE-specific types.

Adds `calls_gitaly` for the `TodoType#body` field, as an error is raised
when requesting the `todo.body field` for a `Commit` `Todo`:

    RuntimeError (Gitaly is called for field 'body' on Types::TodoType
    - please either specify a constant complexity or add
    `calls_gitaly: true` to the field declaration)

When the `Todo` (a polymorphic model) has a `target_type` of `Commit`,
requesting the `body` field calls Gitaly (`Todo#body` calls
`Todo#target` which fetches the `Commit` from Gitaly) and we get the
above error.

I've set `calls_gitaly: true` for the `TodoType#body` field (affecting
all Todos, regardless of the `target_type`) in order to avoid the error,
while we work out a better solution.

https://gitlab.com/gitlab-org/gitlab/issues/34757
https://gitlab.com/gitlab-org/gitlab/issues/34757#note_234752665