KT-7443 Inspection + intention to replace assert (x != null) with "!!" or elvis

#KT-7443 Fixed

j2k/testData/fileOrElement/assertStatement/assertNotNull.java

@@ -0,0 +1,13 @@
+abstract class C {
+    void foo() {
+        String s1 = f();
+        assert s1 != null;
+
+        String s2 = g();
+        assert s2 != null : "g should not return null";
+        int h = s2.hashCode();
+    }
+
+    abstract void f(): String;
+    abstract void g(): String;
+}