Add PSI test templates for identifiers

compiler/tests-spec/testData/psi/templates/identifiers/companionObject.kt

@@ -0,0 +1,17 @@
+class A {
+    companion object <!ELEMENT!> {
+
+    }
+}
+
+class B {
+    companion object <!ELEMENT!>: A() {
+
+    }
+}
+
+class C {
+    companion object <!ELEMENT!>: B by expr, x1, A() {
+
+    }
+}