Improve check for statements-only postfix templates

Before this change the check was quite complicated
because of cases like:
for (i in 1..9)
    foo(i)<caret>

It's not located in a block, but in the same time it's a stament.
So we had a tricky heuristics that if is parent is not a block, then
we should check if element isn't used as expression.

Of course this heuristics is wrong, e.g. for import/package nodes.

The solution is to reuse similar logic from BasicExpressionTypingVisitor.
it has been checked once that statement container is one of:
- KtBlockExpression
- KtContainerNodeForControlStructureBody
- KtWhenEntry

So there's no need to check anything else

 #KT-14986 Fixed
 #KT-14483 Fixed

compiler/frontend/src/org/jetbrains/kotlin/psi/KtPsiUtil.java

@@ -860,4 +860,14 @@ public class KtPsiUtil {
         }
         return deparenthesizedExpression;
     }
+
+    public static boolean isStatementContainer(@Nullable PsiElement container) {
+        return container instanceof KtBlockExpression ||
+               container instanceof KtContainerNodeForControlStructureBody ||
+               container instanceof KtWhenEntry;
+    }
+
+    public static boolean isStatement(@NotNull PsiElement element) {
+        return isStatementContainer(element.getParent());
+    }
 }

compiler/frontend/src/org/jetbrains/kotlin/types/expressions/BasicExpressionTypingVisitor.java

@@ -1681,13 +1681,7 @@ public class BasicExpressionTypingVisitor extends ExpressionTypingVisitor {
             parent = parent.getParent();
         }
 
-        return isParentForBlockLevelExpression(parent);
-    }
-
-    private static boolean isParentForBlockLevelExpression(@Nullable PsiElement parent) {
-        return parent instanceof KtBlockExpression ||
-               parent instanceof KtContainerNodeForControlStructureBody ||
-               parent instanceof KtWhenEntry;
+        return KtPsiUtil.isStatementContainer(parent);
     }
 
     @Override