Move test_semaphores_import_export_fd from cl_khr_semaphore to cl_khr_external_sync_fd related tests

[nikhiljnv]

Some cl_khr_external_sync_fd related tests are currently present in cl_khr_semaphore. https://github.com/KhronosGroup/OpenCL-CTS/blob/f924273cdd607db39e8ff5e1490f5cef87242b7e/test_conformance/extensions/cl_khr_semaphore/test_semaphores.cpp#L651C80-L651C80

May be move these to a separate directory specific to cl_khr_external_sync_fd or cl_khr_external_semaphore at least.