filter: deselect multiarch tests on non-multiarch clusters

Add filter_multiarch_tests() to pytest_collection_modifyitems.
Multiarch-marked tests are deselected on homogeneous clusters,
preventing validate_collected_tests_arch_params from erroring
during collection-only runs (e.g. tox pytest-check-x86).

Signed-off-by: Harel Meir <hmeir@redhat.com>
Co-Authored-By: Claude Sonnet 4.6 (1M context) <noreply@anthropic.com>

Author: hmeir

conftest.py

@@ -33,6 +33,7 @@
 from utilities.bitwarden import get_cnv_tests_secret_by_name
 from utilities.constants import (
     AMD_64,
+    MULTIARCH,
     QUARANTINED,
     SETUP_ERROR,
     TIMEOUT_5MIN,
@@ -558,6 +559,15 @@ def filter_sno_only_tests(items: list[Item], config: Config) -> list[Item]:
     return items
 
 
+def filter_multiarch_tests(items: list[Item], config: Config) -> list[Item]:
+    if py_config.get("cluster_type") == MULTIARCH:
+        return items
+    discard_tests, items_to_return = remove_tests_from_list(items=items, filter_str="multiarch")
+    if discard_tests:
+        config.hook.pytest_deselected(items=discard_tests)
+    return items_to_return
+
+
 def remove_tests_from_list(items: list[Item], filter_str: str) -> tuple[list[Item], list[Item]]:
     discard_tests: list[Item] = []
     items_to_return: list[Item] = []
@@ -635,6 +645,7 @@ def pytest_collection_modifyitems(session, config, items):
         config.hook.pytest_deselected(items=discard)
     items[:] = filter_deprecated_api_tests(items=items, config=config)
     items[:] = filter_sno_only_tests(items=items, config=config)
+    items[:] = filter_multiarch_tests(items=items, config=config)
     items[:] = mark_nmstate_dependent_tests(items=items)