ChainCallJoinLinesHandler: join chained calls; assignment/declaration+call

Fixes IDEA-54209 Join Lines should be able to merge multiple method calls into a chained call

java/java-tests/testData/codeInsight/joinLines/DeclarationAndCall.java

@@ -0,0 +1,8 @@
+class Foo {
+    void test() {
+        <caret>StringBuilder sb = new StringBuilder();
+        sb.append("foo");
+        sb.append("bar");
+        sb.append("baz");
+    }
+}