Fix continuation indentation in while statement (PY-11869).

python/src/com/jetbrains/python/formatter/PyBlock.java

@@ -284,7 +284,8 @@ public class PyBlock implements ASTBlock {
            psi instanceof PyFunction ||
            psi instanceof PyTryExceptStatement ||
            psi instanceof PyElsePart ||
-           psi instanceof PyIfPart;
+           psi instanceof PyIfPart ||
+           psi instanceof PyWhileStatement;
   }
 
   private static boolean isSubscriptionOperand(ASTNode child) {

python/testData/formatter/continuationIndentInIndentingStatement.py

@@ -28,4 +28,8 @@ try:
     pass
 except \
     AttributeError:
-    pass
+    pass
+
+while value \
+    in values:  # <- missing continuation indent here
+    do_smth()

python/testData/formatter/continuationIndentInIndentingStatement_after.py

@@ -28,4 +28,8 @@ try:
     pass
 except \
         AttributeError:
-    pass
+    pass
+
+while value \
+        in values:  # <- missing continuation indent here
+    do_smth()