Added the --app-pid flag to the python matter testing support (project-chip#31866)

* Added the --app-pid flag to the python matter testing support to provide a way for test scripts to get the PID of the app they are running against.

* fixed typo.

Co-authored-by: Petru Lauric <81822411+plauric@users.noreply.github.com>

---------

Co-authored-by: Petru Lauric <81822411+plauric@users.noreply.github.com>

Author: hicklin

src/python_testing/matter_testing_support.py

@@ -303,6 +303,7 @@ class MatterTestConfig:
     tests: List[str] = field(default_factory=list)
     timeout: typing.Union[int, None] = None
     endpoint: int = 0
+    app_pid: int = 0
 
     commissioning_method: Optional[str] = None
     discriminators: Optional[List[int]] = None
@@ -1244,6 +1245,7 @@ def convert_args_to_matter_config(args: argparse.Namespace) -> MatterTestConfig:
     config.tests = [] if args.tests is None else args.tests
     config.timeout = args.timeout  # This can be none, we pull the default from the test if it's unspecified
     config.endpoint = 0 if args.endpoint is None else args.endpoint
+    config.app_pid = 0 if args.app_pid is None else args.app_pid
 
     config.controller_node_id = args.controller_node_id
     config.trace_to = args.trace_to
@@ -1296,6 +1298,7 @@ def parse_matter_test_args(argv: List[str]) -> MatterTestConfig:
                              help='Node ID for primary DUT communication, '
                              'and NodeID to assign if commissioning (default: %d)' % _DEFAULT_DUT_NODE_ID, nargs="+")
     basic_group.add_argument('--endpoint', type=int, default=0, help="Endpoint under test")
+    basic_group.add_argument('--app-pid', type=int, default=0, help="The PID of the app against which the test is going to run")
     basic_group.add_argument('--timeout', type=int, help="Test timeout in seconds")
     basic_group.add_argument("--PICS", help="PICS file path", type=str)