Implements #120

1. Removed dpctl.memory
2. Exposed MemoryUSMShared, MemoryUSMDevice, MemoryUSMHost to dpctl
3. When dpctl is cimported MemoryUSMShared, MemoryUSMHost, MemoryUSMDevice
   and Memory classes are exposed.

Author: oleksandr-pavlyk

dpctl/__init__.pxd

@@ -28,3 +28,5 @@
 # cython: language_level=3
 
 from dpctl._sycl_core cimport *
+from dpctl._memory import *
+

dpctl/__init__.py

@@ -47,6 +47,7 @@
 __author__ = "Intel Corp."
 
 from ._sycl_core import *
+from ._memory import MemoryUSMShared, MemoryUSMDevice, MemoryUSMHost
 from ._version import get_versions
 
 

dpctl/memory.py

@@ -23,14 +23,13 @@
 ##===----------------------------------------------------------------------===##
 
 import dpctl
-import dpctl.memory
 import unittest
 
 
 class TestQueueMemcpy(unittest.TestCase):
     def _create_memory(self):
         nbytes = 1024
-        mobj = dpctl.memory.MemoryUSMShared(nbytes)
+        mobj = dpctl.MemoryUSMShared(nbytes)
         return mobj
 
     @unittest.skipUnless(