graphql types: add TransactionData enum, rename Transaction to TransactionDataV1

```Rust
pub struct Event {
    pub package_id: ObjectId,
    pub module: Identifier,
```

```Rust
pub struct Event {
    pub package_id: ObjectID,
    pub transaction_module: Identifier,
```
iota repo has `transaction_` as name, is this fine or do we want to align?

