PY-21350 Fixed: Wrong return type for input() in Python 3

Add skeletons for raw_input() in Python 2 and input() for both Pythons.
Update PyUserSkeletonsTypeProvider to wrap callable's return type even if it's null.

python/testSrc/com/jetbrains/python/Py3TypeTest.java

@@ -443,7 +443,7 @@ public class Py3TypeTest extends PyTestCase {
 
   // PY-20073
   public void testMapReturnType() {
-    doTest("int", 
+    doTest("int",
            "for x in map(lambda x: 42, 'foo'):\n" +
            "    expr = x");
   }
@@ -459,6 +459,12 @@ public class Py3TypeTest extends PyTestCase {
            "expr = get_value([])");
   }
 
+  // PY-21350
+  public void testBuiltinInput() {
+    doTest("str",
+           "expr = input()");
+  }
+
   private void doTest(final String expectedType, final String text) {
     myFixture.configureByText(PythonFileType.INSTANCE, text);
     final PyExpression expr = myFixture.findElementByText("expr", PyExpression.class);

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

@@ -1416,6 +1416,18 @@ public class PyTypeTest extends PyTestCase {
            "expr = get_value([])");
   }
 
+  // PY-21350
+  public void testBuiltinInput() {
+    doTest("Any",
+           "expr = input()");
+  }
+
+  // PY-21350
+  public void testBuiltinRawInput() {
+    doTest("str",
+           "expr = raw_input()");
+  }
+
   private static List<TypeEvalContext> getTypeEvalContexts(@NotNull PyExpression element) {
     return ImmutableList.of(TypeEvalContext.codeAnalysis(element.getProject(), element.getContainingFile()).withTracing(),
                             TypeEvalContext.userInitiated(element.getProject(), element.getContainingFile()).withTracing());

python/testSrc/com/jetbrains/python/inspections/Py3TypeCheckerInspectionTest.java

@@ -178,4 +178,9 @@ public class Py3TypeCheckerInspectionTest extends PyTestCase {
   public void testMapArgumentsInOppositeOrder() {
     doTest();
   }
+
+  // PY-21350
+  public void testBuiltinInputPy3() {
+    doTest();
+  }
 }

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

@@ -350,4 +350,14 @@ public class PyTypeCheckerInspectionTest extends PyTestCase {
   public void testPositionalArguments() {
     doTest();
   }
+
+  // PY-21350
+  public void testBuiltinInputPy2() {
+    doTest();
+  }
+
+  // PY-21350
+  public void testBuiltinRawInput() {
+    doTest();
+  }
 }