Fix header scope for secondary constructors

Add companion object's scope and nested classes

 #KT-6996 fixed

compiler/testData/diagnostics/tests/secondaryConstructors/companionObjectScope.kt

@@ -0,0 +1,17 @@
+// !DIAGNOSTICS: -UNUSED_PARAMETER
+class A {
+    companion object {
+        fun foo(): Int = 1
+        val prop = 2
+        val C = 3
+    }
+    object B {
+        fun bar(): Int = 4
+        val prop = 5
+    }
+    object C {
+    }
+
+    constructor(x: Int) {}
+    constructor() : this(foo() + prop + B.bar() + B.prop + C) {}
+}