get_device_cached_queue now supports filter selector strings

```

In [1]: import dpctl

In [2]: import dpctl._sycl_queue_manager as qm

In [3]: qm.__pyx_capi__
Out[3]:
{'get_current_queue': <capsule object "struct PySyclQueueObject *(int __pyx_skip_dispatch)" at 0x7fe2260bcc30>,
 'get_current_device_type': <capsule object "PyObject *(int __pyx_skip_dispatch)" at 0x7fe2260bcc60>,
 'get_current_backend': <capsule object "PyObject *(int __pyx_skip_dispatch)" at 0x7fe2260bcc90>,
 'get_device_cached_queue': <capsule object "PyObject *(PyObject *, int __pyx_skip_dispatch)" at 0x7fe2260bccc0>}

In [4]: qm.get_device_cached_queue("cpu")
Out[4]: <dpctl.SyclQueue at 0x7fe226945b80>

In [5]: qm.get_device_cached_queue("gpu")
Out[5]: <dpctl.SyclQueue at 0x7fe21c032ec0>
```

Author: oleksandr-pavlyk

dpctl/_sycl_queue_manager.pyx

@@ -310,6 +310,9 @@ cdef class _DeviceDefaultQueueCache:
         elif isinstance(key, SyclDevice):
             q = SyclQueue(key)
             ctx_dev = q.sycl_context, key
+        elif isinstance(key, str):
+            q = SyclQueue(key)
+            ctx_dev = q.sycl_context, q.sycl_device
         else:
             raise TypeError
         if ctx_dev in self.__device_queue_map__: