workgroups: fix program/kernel object leak

`create_single_kernel_helper` is called in a loop, overwriting the
objects contained in the wrapper classes.  The wrapper class is not
aware of this, as the overwriting happens through its `operator&`.

Move the wrapper objects into the loop, so that the contained objects
get released as soon as the program and kernel objects are no longer
needed.

Signed-off-by: Sven van Haastregt <sven.vanhaastregt@arm.com>

test_conformance/workgroups/test_wg_suggested_local_work_size.cpp

@@ -221,8 +221,6 @@ int do_test_work_group_suggested_local_size(
  bool (*skip_cond)(size_t), size_t start, size_t end, size_t incr,
  cl_long max_local_mem_size, size_t global_work_offset[], num_dims dim)
 {
- clProgramWrapper scan_program;
- clKernelWrapper scan_kernel;
  int err;
  size_t test_values[] = { 1, 1, 1 };
  std::string kernel_names[6] = {
@@ -244,6 +242,8 @@ int do_test_work_group_suggested_local_size(
  for (int kernel_num = 0; kernel_num < 6; kernel_num++)
  {
  if (max_local_mem_size < local_mem_size[kernel_num]) continue;
+ clProgramWrapper scan_program;
+ clKernelWrapper scan_kernel;
  // Create the kernel
  err = create_single_kernel_helper(
  context, &scan_program, &scan_kernel, 1,