StreamApiMigration: collect(joining()): allow separator addition based on counting loop variable value

java/java-tests/testData/codeInsight/daemonCodeAnalyzer/quickFix/streamApiMigration/afterJoiningUsingIndex.java

@@ -0,0 +1,11 @@
+// "Replace with collect" "true"
+
+import java.util.List;
+import java.util.stream.Collectors;
+
+public class Test {
+  public void test(List<String> list) {
+      String sb = list.stream().limit(10).collect(Collectors.joining(","));
+      System.out.println(sb);
+  }
+}

java/java-tests/testData/codeInsight/daemonCodeAnalyzer/quickFix/streamApiMigration/beforeJoiningUsingIndex.java

@@ -0,0 +1,14 @@
+// "Replace with collect" "true"
+
+import java.util.List;
+
+public class Test {
+  public void test(List<String> list) {
+    StringBuilder sb = new StringBuilder();
+    for (int <caret>i=0; i<Math.min(10, list.size()); i++) {
+      if(i > 0) sb.append(",");
+      sb.append(list.get(i));
+    }
+    System.out.println(sb.toString());
+  }
+}