Support __class_getitem__ (PY-27913)

Update resolve for `[]` on definitions so `__class_getitem__` is supported.
Support this method (and `__mro_entries__`) in highlighting and completion.
Process it as a static method.

python/testSrc/com/jetbrains/python/PyTypeTest.java

@@ -2348,6 +2348,17 @@ public class PyTypeTest extends PyTestCase {
     );
   }
 
+  // PY-27913
+  public void testDunderClassGetItemFirstParameter() {
+    runWithLanguageLevel(
+      LanguageLevel.PYTHON37,
+      () -> doTest("Type[Foo]",
+                   "class Foo:\n" +
+                   "    def __class_getitem__(cls, item):\n" +
+                   "        expr = cls")
+    );
+  }
+
   public void testNoneLiteral() {
     runWithLanguageLevel(
       LanguageLevel.PYTHON34,

python/testSrc/com/jetbrains/python/PythonCompletionTest.java

@@ -1211,6 +1211,19 @@ public class PythonCompletionTest extends PyTestCase {
     );
   }
 
+  // PY-27913
+  public void testDunderClassGetItem() {
+    runWithLanguageLevel(
+      LanguageLevel.PYTHON37,
+      () -> {
+        final List<String> suggested = doTestByText("class A:\n" +
+                                                    "    def __<caret>");
+        assertNotNull(suggested);
+        assertContainsElements(suggested, "__class_getitem__(cls, item)");
+      }
+    );
+  }
+
   @Override
   protected String getTestDataPath() {
     return super.getTestDataPath() + "/completion";

python/testSrc/com/jetbrains/python/PythonHighlightingTest.java

@@ -391,6 +391,11 @@ public class PythonHighlightingTest extends PyTestCase {
     doTest(LanguageLevel.PYTHON37, false, false);
   }
 
+  // PY-27913
+  public void testDunderClassGetItem() {
+    doTest(LanguageLevel.PYTHON37, false, true);
+  }
+
   @NotNull
   private static EditorColorsScheme createTemporaryColorScheme() {
     EditorColorsManager manager = EditorColorsManager.getInstance();

python/testSrc/com/jetbrains/python/PythonInspectionsTest.java

@@ -54,6 +54,10 @@ public class PythonInspectionsTest extends PyTestCase {
     doHighlightingTest(PyMethodParametersInspection.class, LanguageLevel.PYTHON36);
   }
 
+  public void testPyMethodParametersInspectionClassGetItem() {
+    doHighlightingTest(PyMethodParametersInspection.class, LanguageLevel.PYTHON37);
+  }
+
   public void testPyNestedDecoratorsInspection() {
     LocalInspectionTool inspection = new PyNestedDecoratorsInspection();
     doTest(getTestName(false), inspection);

python/testSrc/com/jetbrains/python/inspections/PyUnresolvedReferencesInspectionTest.java

@@ -670,6 +670,11 @@ public class PyUnresolvedReferencesInspectionTest extends PyInspectionTestCase {
     doMultiFileTest();
   }
 
+  // PY-27913
+  public void testDunderClassGetItem() {
+    runWithLanguageLevel(LanguageLevel.PYTHON37, this::doTest);
+  }
+
   @NotNull
   @Override
   protected Class<? extends PyInspection> getInspectionClass() {