Clang: Move createJobRequest into Jobs

This simplifies the high level client ClangCodeModelServer and removes
quite some duplication in tests.

Change-Id: I4c6ab8646c8728990ebaca2b920ae514e949c54a
Reviewed-by: David Schulz <david.schulz@qt.io>

src/tools/clangbackend/ipcsource/clangjobrequest.h

@@ -93,9 +93,6 @@ public:
 };
 
 using JobRequests = QVector<JobRequest>;
-using JobRequestCreator = std::function<JobRequest(const Document &,
-                                                   JobRequest::Type ,
-                                                   PreferredTranslationUnit)>;
 
 QDebug operator<<(QDebug debug, const JobRequest &jobRequest);