Fix lifetime of pointer used in update

When we initialize our `ze_mutable_group_count_exp_desc_t` struct that's
used in a pointer chain passed to
`zexCommandListUpdateMutableCommandsExp` we set the
`pGroupCount` member to `&ZeThreadGroupDimensions`.

However, `ZeThreadGroupDimensions` is declared on the stack in the
scope of the if statement. Resulting in this pointer becoming invalid
after the scope of the if statement, when the L0 update API is called.

Fixed by moving the `ZeThreadGroupDimensions` variable outside the
scope of the if statement, into the scope of the function, so that
the address is valid when `zexCommandListUpdateMutableCommandsExp`
is called.

Author: EwanC

source/adapters/level_zero/command_buffer.cpp

@@ -1278,8 +1278,9 @@ UR_APIEXPORT ur_result_t UR_APICALL urCommandBufferUpdateKernelLaunchExp(
   UR_ASSERT(!(NewGlobalWorkSize && !NewLocalWorkSize) ||
                 (SupportedFeatures & ZE_MUTABLE_COMMAND_EXP_FLAG_GROUP_SIZE),
             UR_RESULT_ERROR_UNSUPPORTED_FEATURE);
+
+  ze_group_count_t ZeThreadGroupDimensions{1, 1, 1};
   if (NewGlobalWorkSize && Dim > 0) {
-    ze_group_count_t ZeThreadGroupDimensions{1, 1, 1};
     uint32_t WG[3];
     // If new global work size is provided but new local work size is not
     // provided then we still need to update local work size based on size