TTL API for creating global/local memory fence

Hey,
I'm using TTL API for Import/Export memory transactions.
However, In some cases I need the option to create global memory fence
between some transactions. and for this case I need to use
```
async_work_group_copy_fence(CLK_GLOBAL_MEM_FENCE)
```
would be nicer to have this memory fence in TTL API with an input of the memory type.

Thanks in advance,

Start by reviewing the TTL API used for Import/Export memory transactions and the OpenCL C async_work_group_copy_fence(CLK_GLOBAL_MEM_FENCE) call cited here. Determine how global and local memory types should be represented in the API and what behavior is required between transactions. Done means the fence capability and its memory-type input are clearly defined and implemented.

Written by the indexing model from the issue text.