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) {}
+}

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

@@ -0,0 +1,35 @@
+package
+
+internal final class A {
+    public constructor A()
+    public constructor A(/*0*/ x: kotlin.Int)
+    public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+
+    internal object B {
+        private constructor B()
+        internal final val prop: kotlin.Int = 5
+        internal final fun bar(): kotlin.Int
+        public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+        public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+        public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+    }
+
+    internal object C {
+        private constructor C()
+        public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+        public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+        public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+    }
+
+    internal companion object Companion {
+        private constructor Companion()
+        internal final val C: kotlin.Int = 3
+        internal final val prop: kotlin.Int = 2
+        public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+        internal final fun foo(): kotlin.Int
+        public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+        public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+    }
+}