fix(tests): drop stale __contains__ references after ABC removal

Roborev #1761: the ``required = {...}`` set in
``test_program_cache_resource_requires_core_methods`` still
contained ``"__contains__"`` after the prior commit removed it
from the ABC, which would fail the assertion immediately. Drop it
from the required set, add a positive assertion that
``__contains__`` is intentionally NOT abstract (with a comment
explaining why), and remove the now-vestigial ``__contains__``
methods from the ``_Empty`` and ``_Tracked`` test subclasses.

Author: cpcloud

cuda_core/tests/test_program_cache.py

@@ -22,12 +22,15 @@ def test_program_cache_resource_requires_core_methods():
     required = {
         "__getitem__",
         "__setitem__",
-        "__contains__",
         "__delitem__",
         "__len__",
         "clear",
     }
     assert required <= ProgramCacheResource.__abstractmethods__
+    # ``__contains__`` is intentionally NOT abstract: the racy
+    # ``key in cache; data = cache[key]`` idiom should be discouraged
+    # in favour of ``data = cache.get(key)``.
+    assert "__contains__" not in ProgramCacheResource.__abstractmethods__
 
 
 def _build_empty_subclass():
@@ -40,9 +43,6 @@ def __getitem__(self, key):
         def __setitem__(self, key, value):
             pass
 
-        def __contains__(self, key):
-            return False
-
         def __delitem__(self, key):
             raise KeyError(key)
 
@@ -83,9 +83,6 @@ def __getitem__(self, key):
         def __setitem__(self, key, value):
             pass
 
-        def __contains__(self, key):
-            return False
-
         def __delitem__(self, key):
             raise KeyError(key)