Can't generate ForwardDISET requests for calls from DiracX

```
Error while sending the job status ValueError('No dirax token in the proxy file /tmp/condor_execute/dir_77954/tmpasa9c8bf')
2024-01-18T09:57:43,016657Z None/[7886]JobWrapper WARN: JobReportFailure Could not generate a forwardDISET operation: Could not create ForwardDISET operation
2024-01-18T09:57:43,016711Z None/[7886]JobWrapper WARN: JobReportFailure The job won't fail, but the jobLogging info might be incomplete
2024-01-18T09:57:43,016748Z None/[7886]JobWrapper INFO: Job finished successfully with no pending requests
```

We use the rpcStub as part of generating the forward diset request but this doesn't exist when using the legacy adapter:

https://github.com/DIRACGrid/DIRAC/blob/bfb0f6712cc7fe12b903852a82fe0d30ec7dcac8/src/DIRAC/WorkloadManagementSystem/Client/JobReport.py#L144-L161

To reach that:
* [x] make an RPC stub equivalent for DiracX
* [x] Modify `ForwardDISET` to execute it
* [ ] generate the stub where needed