Use unique_ptr to manage lifetime of new copy of sycl::queue

This simplifies the code, and is in line with C++ coding practices.
Thanks @AlexanderKalistratov for the suggestion.

Author: oleksandr-pavlyk

dpctl/apis/include/dpctl4pybind11.hpp

@@ -759,8 +759,9 @@ class usm_memory : public py::object
     {
         auto const &api = ::dpctl::detail::dpctl_capi::get();
         DPCTLSyclUSMRef usm_ref = reinterpret_cast<DPCTLSyclUSMRef>(usm_ptr);
-        sycl::queue *q_ptr = new sycl::queue(q);
-        DPCTLSyclQueueRef QRef = reinterpret_cast<DPCTLSyclQueueRef>(q_ptr);
+        auto q_uptr = std::make_unique<sycl::queue>(q);
+        DPCTLSyclQueueRef QRef =
+            reinterpret_cast<DPCTLSyclQueueRef>(q_uptr.get());
 
         auto vacuous_destructor = []() {};
         py::object mock_owner = py::capsule(vacuous_destructor);
@@ -784,7 +785,6 @@ class usm_memory : public py::object
             }
             if (eptr) {
                 Py_DECREF(_memory);
-                delete q_ptr;
                 std::rethrow_exception(eptr);
             }
             Py_MemoryObject *memobj =
@@ -799,9 +799,9 @@ class usm_memory : public py::object
             // std::shared_ptr and the deleter of the shared_ptr<void> is
             // supposed to free the USM allocation
             m_ptr = _memory;
+            q_uptr.release();
         }
         else {
-            delete q_ptr;
             Py_DECREF(_memory);
 
             throw std::runtime_error(