[OpenCL validation] OpenCL 1.2 barrier instructions

For the Barrier Instructions **OpControlBarrier** and **OpMemoryBarrier**, the _Scope_ for _Execution_ must be _Workgroup_, the _Scope_ for _Memory_ must be _Workgroup_, and the _Memory Semantics_ must
be _SequentiallyConsistent_.

Start by locating the validation logic for the OpenCL 1.2 barrier instructions OpControlBarrier and OpMemoryBarrier. Check how their execution scope, memory scope, and memory semantics are validated; done means the required Workgroup and SequentiallyConsistent constraints are enforced.

Written by the indexing model from the issue text.