allow variable introduction inside lambda chain with expression -> block lambda conversion

java/java-tests/testData/refactoring/introduceVariable/PutInNestedLambdaBody.after.java

@@ -0,0 +1,10 @@
+import java.util.function.Function;
+class Test {
+
+  Function<String, Runnable> f = (str) -> () -> {
+      String s = "";
+      foo(s);
+  };
+
+  void foo(String s) {}
+}