Fix the device used by KernelExecutionFixture (#2344)

Fix KernelExecutionFixture to use the device associated to the queue, when a queue
is passed as argument, instead of always using the first device.

Note that, if the Platform is not stateless (e.g. with SYCL), the platform data
member is still wrong. However, there is no way to access the platform associated
to a device object.
Since the platform object will not be used, ignore this issue for the time being.

include/alpaka/test/KernelExecutionFixture.hpp

@@ -44,13 +44,20 @@ namespace alpaka::test
         {
         }
 
-        KernelExecutionFixture(Queue queue, WorkDiv workDiv) : m_queue{std::move(queue)}, m_workDiv{std::move(workDiv)}
+        KernelExecutionFixture(Queue queue, WorkDiv workDiv)
+            : m_platform{} // if the platform is not stateless, this is wrong; we ignore it because it is not be used
+            , m_device{alpaka::getDev(queue)}
+            , m_queue{std::move(queue)}
+            , m_workDiv{std::move(workDiv)}
         {
         }
 
         template<typename TExtent>
-        KernelExecutionFixture(Queue queue, TExtent const& extent) : m_queue{std::move(queue)}
-                                                                   , m_extent{extent}
+        KernelExecutionFixture(Queue queue, TExtent const& extent)
+            : m_platform{} // if the platform is not stateless, this is wrong; we ignore it because it is not be used
+            , m_device{alpaka::getDev(queue)}
+            , m_queue{std::move(queue)}
+            , m_extent{extent}
         {
         }