twister: pytest: Allow using pytest-args from command file and yaml

Extend pytest-args from configuration yaml file with args
from command line instead of overwriting.

Signed-off-by: Grzegorz Chwierut <grzegorz.chwierut@nordicsemi.no>

doc/develop/test/pytest.rst

@@ -97,6 +97,8 @@ There are two ways for passing extra arguments to the called pytest subprocess:
       -s samples/subsys/testsuite/pytest/shell/sample.pytest.shell \
       --pytest-args='-k test_shell_print_version'
 
+   The command line arguments will extend those from the .yaml file. If the same argument is
+   present in both places, the one from the command line will take precedence.
 
 Fixtures
 ********

scripts/pylib/twister/twisterlib/environment.py

@@ -234,7 +234,7 @@ Artificially long but functional example:
     parser.add_argument(
         "--pytest-args", action="append",
         help="""Pass additional arguments to the pytest subprocess. This parameter
-        will override the pytest_args from the harness_config in YAML file.
+        will extend the pytest_args from the harness_config in YAML file.
         """)
 
     valgrind_asan_group.add_argument(

scripts/pylib/twister/twisterlib/harness.py

@@ -421,11 +421,7 @@ class Pytest(Harness):
 
         if handler.options.pytest_args:
             command.extend(handler.options.pytest_args)
-            if pytest_args_yaml:
-                logger.warning(f'The pytest_args ({handler.options.pytest_args}) specified '
-                               'in the command line will override the pytest_args defined '
-                               f'in the YAML file {pytest_args_yaml}')
-        else:
+
         command.extend(pytest_args_yaml)
 
         return command

scripts/tests/twister/pytest_integration/test_harness_pytest.py

@@ -74,7 +74,7 @@ def test_pytest_command_extra_args(testinstance: TestInstance):
 
 def test_pytest_command_extra_args_in_options(testinstance: TestInstance):
     pytest_harness = Pytest()
-    pytest_args_from_yaml = '-k test_from_yaml'
+    pytest_args_from_yaml = '--extra-option'
     pytest_args_from_cmd = ['-k', 'test_from_cmd']
     testinstance.testsuite.harness_config['pytest_args'] = [pytest_args_from_yaml]
     testinstance.handler.options.pytest_args = pytest_args_from_cmd
@@ -82,7 +82,7 @@ def test_pytest_command_extra_args_in_options(testinstance: TestInstance):
     command = pytest_harness.generate_command()
     assert pytest_args_from_cmd[0] in command
     assert pytest_args_from_cmd[1] in command
-    assert pytest_args_from_yaml not in command
+    assert pytest_args_from_yaml in command
 
 
 @pytest.mark.parametrize(