Added support for python -m dpctl -l to list platforms

```
(dev_dpctl) opavlyk@opavlyk-mobl:~/repos/dpctl$ python -m dpctl --help
usage: __main__.py [-h] [--includes] [--cmakedir] [--library] [-l] [-e] [-s]

optional arguments:
  -h, --help       show this help message and exit
  --includes       Include flags dpctl headers.
  --cmakedir       CMake module directory, ideal for setting -DDPCTL_ROOT in CMake.
  --library        Linker flags for SyclInterface library.
  -l, --full-list  Enumerate system platforms, using dpctl.lsplatform(verbosity=2)
  -e, --long-list  Enumerate system platforms, using dpctl.lsplatform(verbosity=1)
  -s, --summary    Enumerate system platforms, using dpctl.lsplatform()
```

Author: oleksandr-pavlyk

dpctl/__main__.py

@@ -19,6 +19,7 @@
 import os.path
 import platform
 import sys
+import warnings
 
 import dpctl
 
@@ -50,6 +51,24 @@ def print_library() -> None:
     print(ld_flags + " -lSyclInterface")
 
 
+def _warn_if_any_set(args, li) -> None:
+    opts_set = [it for it in li if getattr(args, it, True)]
+    if opts_set:
+        if len(opts_set) == 1:
+            warnings.warn(
+                "The option " + str(opts_set[0]) + " is being ignored.",
+                stacklevel=3,
+            )
+        else:
+            warnings.warn(
+                "Options " + str(opts_set) + " are being ignored.", stacklevel=3
+            )
+
+
+def print_lsplatform(verbosity: int) -> None:
+    dpctl.lsplatform(verbosity=verbosity)
+
+
 def main() -> None:
     """Main entry-point."""
     parser = argparse.ArgumentParser()
@@ -68,9 +87,45 @@ def main() -> None:
         action="store_true",
         help="Linker flags for SyclInterface library.",
     )
+    parser.add_argument(
+        "-l",
+        "--full-list",
+        action="store_true",
+        help="Enumerate system platforms, using dpctl.lsplatform(verbosity=2)",
+    )
+    parser.add_argument(
+        "-e",
+        "--long-list",
+        action="store_true",
+        help="Enumerate system platforms, using dpctl.lsplatform(verbosity=1)",
+    )
+    parser.add_argument(
+        "-s",
+        "--summary",
+        action="store_true",
+        help="Enumerate system platforms, using dpctl.lsplatform()",
+    )
     args = parser.parse_args()
     if not sys.argv[1:]:
         parser.print_help()
+    if args.full_list:
+        _warn_if_any_set(
+            args, ["long_list", "summary", "includes", "cmakedir", "library"]
+        )
+        print_lsplatform(2)
+        return
+    if args.long_list:
+        _warn_if_any_set(
+            args, ["full_list", "summary", "includes", "cmakedir", "library"]
+        )
+        print_lsplatform(1)
+        return
+    if args.summary:
+        _warn_if_any_set(
+            args, ["long_list", "full_list", "includes", "cmakedir", "library"]
+        )
+        print_lsplatform(0)
+        return
     if args.includes:
         print_includes()
     if args.cmakedir: