Pass contextId in ProcessRequest struct instead to passing it as parameter of the ProcessBatchV2 function

[agnusmor]

In PR #3604 we added the possibility to pass a contextId value to the ProcessBatchV2 function to add end-2-end tracking of the sequencer-executor requests. Reviewing it we think it's better to pass this contextId value as parameter of the ProcessRequest struct instead as parameter of the function ProcessBatchV2.