Added _runner utility file to examples/python

Used run_examples routine implemented in _runner that
support comand-line arguments, allows introspect available
examples and run all of them, or any subset individually.

E.g.

```
(idp) [09:37:14 nuc04 python]$ python subdevices.py -q --run subdivide_root_cpu_device

cpu_d is a root device.
Sub-device #EU:  [4, 4, 4]
Sub-device is_root:  [False, False, False]
Sub-device parent is what we expected:  [True, True, True]
Sub-sub-device #EU:  [[1, 3], [1, 3], [1, 3]]
```

Author: oleksandr-pavlyk

examples/python/_runner.py

@@ -0,0 +1,67 @@
+import argparse
+import inspect
+
+
+def has_nondefault_params(sgn):
+    for v in sgn.parameters.values():
+        if v.default is inspect._empty:
+            return True
+    return False
+
+
+def run_examples(example_description, glbls_dict):
+    parser = argparse.ArgumentParser(
+        description=example_description,
+    )
+    parser.add_argument(
+        "-r",
+        "--run",
+        type=str,
+        help="Functions to execute. Use --run all to run all of them.",
+    )
+    parser.add_argument(
+        "-l", "--list", action="store_true", help="List available function names to run"
+    )
+    parser.add_argument(
+        "-q", "--quiet", action="store_true", help="Do not echo example name."
+    )
+    args = parser.parse_args()
+
+    if args.list or not args.run:
+        fns = []
+        for n in glbls_dict:
+            if inspect.isfunction(glbls_dict.get(n)):
+                fns.append(n)
+        if fns:
+            print("Available examples:")
+            print(", ".join(fns))
+        else:
+            print("No examples are availble.")
+        exit(0)
+    if args.run == "all":
+        fns = []
+        for n in glbls_dict:
+            if inspect.isfunction(glbls_dict.get(n)):
+                fns.append(n)
+        args.run = fns
+    else:
+        args.run = args.run.split()
+
+    if args.run:
+        for fn in args.run:
+            if fn in glbls_dict:
+                clbl = glbls_dict.get(fn)
+                sgn = inspect.signature(clbl)
+                print("")
+                if has_nondefault_params(sgn):
+                    if not args.quiet:
+                        print(f"INFO: Skip exectution of {fn} as it requires arguments")
+                else:
+                    if not args.quiet:
+                        print(f"INFO: Executing example {fn}")
+                    clbl()
+                    if not args.quiet:
+                        print("INFO: ===========================")
+
+    else:
+        raise ValueError("No function to run was specified")

examples/python/device_selection.py

@@ -21,6 +21,7 @@
 
 
 def print_device(d):
+    "Display information about given device argument."
     if type(d) is not dpctl.SyclDevice:
         raise ValueError
     print("Name: ", d.name)
@@ -94,4 +95,12 @@ def custom_select_device():
             selected_dev = d
     if selected_dev:
         print_device(selected_dev)
+    else:
+        print("No device with half-precision support is available.")
     return selected_dev
+
+
+if __name__ == "__main__":
+    import _runner as runner
+
+    runner.run_examples("Device selection examples for dpctl.", globals())

examples/python/subdevices.py

@@ -64,8 +64,15 @@ def subdivide_by_affinity(affinity="numa"):
     Create sub-devices partitioning by affinity.
     """
     cpu_d = dpctl.SyclDevice("cpu")
-    sub_devs = cpu_d.create_sub_devices(partition=affinity)
-    return sub_devs
+    try:
+        sub_devs = cpu_d.create_sub_devices(partition=affinity)
+        print(
+            "{} sub-devices were created with #EUs".format(
+                len(sub_devs), [d.max_compute_units for d in sub_devs]
+            )
+        )
+    except:
+        print("Device partitioning by affinity was not successful.")
 
 
 def create_subdevice_queue():
@@ -99,9 +106,6 @@ def create_subdevice_queue():
 
 
 if __name__ == "__main__":
-    print("")
-    print("Executing subdivide_root_cpu_device:")
-    subdivide_root_cpu_device()
-    print("")
-    print("Exectuting create_subdevice_queue:")
-    print(create_subdevice_queue())
+    import _runner as runner
+
+    runner.run_examples("Examples for working with subdevices in dpctl.", globals())