Resolve "Refactor Methods in RequestTableService"

Moved the methods in RequestTableService into different services that the methods fit in better.

Changed:

• SessionStatusService -> labreqCounts added from reqtableservice
• RoleDTOService -> getAssistantsFromeditions added from reqtableservice
• LabService -> getSessionDetailsFromLabs (from ReqTableService), getLabsFromEditions (from ReqTableService)
• AssignmentService created -> countRequestsPerAssignment (from EditionStatusService), getAssignmentsFromEditions (from ReqTableService), assignmentsWithCourseCodes (from ReqTableService) -> more methods from LabService can be added to make LabService shorter
• RoomDTOService -> getRoomsFromSessions added (from requestTableService)

Closes #695