Move flaky option to top level (#2642)

* Add flaky option on top level

* Add newsfragment

Author: kclowes

newsfragments/2642.bugfix.rst

@@ -0,0 +1 @@
+Move ``flaky`` option to top-level conftest.py

tests/conftest.py

@@ -20,3 +20,7 @@ def address_conversion_func(request):
 @pytest.fixture()
 def open_port():
     return get_open_port()
+
+
+def pytest_addoption(parser):
+    parser.addoption("--flaky", action="store_true")

tests/integration/conftest.py

@@ -21,10 +21,6 @@
 # --- integration test configurations --- #
 
 
-def pytest_addoption(parser):
-    parser.addoption("--flaky", action="store_true")
-
-
 def pytest_collection_modifyitems(items, config):
     """
     It is ideal to keep this configuration as simple as possible so that we don't