Kotlin: Add more type check tests for MissingInstanceofInEquals query

Author: tamasvajk

java/ql/test/kotlin/query-tests/MissingInstanceofInEquals/MissingInstanceofInEquals.expected

@@ -0,0 +1,2 @@
+| Test.kt:0:0:0:0 | equals | equals() method does not seem to check argument type. |
+| Test.kt:4:14:6:5 | equals | equals() method does not seem to check argument type. |

java/ql/test/kotlin/query-tests/MissingInstanceofInEquals/MissingInstanceofInEquals.qlref

@@ -0,0 +1 @@
+Likely Bugs/Comparison/MissingInstanceofInEquals.ql

java/ql/test/kotlin/query-tests/MissingInstanceofInEquals/Test.kt

@@ -0,0 +1,7 @@
+data class D(val x: Int) {}
+
+data class E(val x: Int) {
+    override fun equals(other: Any?): Boolean {
+        return (other as? E)?.x == this.x
+    }
+}