New “transactionValidation” graphql subscription API

### Describe the solution you'd like
This subscription should replace both `transactionConfirmed(address: Address!): TransactionAttestation` and `transactionError(address: Address!): TransactionError`.

`transactionValidation` sends notification when transaction validation is done (either on a failure or success).

```typescript
/// On success
{
address: Address,
success: {
crossValidationStamps: [
{
nodePublicKey: PublicKey,
signature: Hex
},
],
},
}

/// On Failure
{
address: Address,
failure: {
context: ErrorContext,
error: ErrorDetails
}
}
```