Refactor DelegationResolver so that lazy and eager resolve share the code

Also fix an exception in LazyClassMemberScope

compiler/testData/loadKotlin/fun/DeclaredMemberOverridesDelegated.kt

@@ -0,0 +1,13 @@
+package test
+
+trait X {
+    fun foo()
+}
+
+trait Y : X {
+}
+
+class B(val a: X) : X by a, Y {
+    override fun foo() {
+    }
+}

compiler/testData/loadKotlin/fun/DeclaredMemberOverridesDelegated.txt

@@ -0,0 +1,16 @@
+package test
+
+internal final class B : test.X, test.Y {
+    /*primary*/ public constructor B(/*0*/ a: test.X)
+    internal final val a: test.X
+        internal final fun <get-a>(): test.X
+    internal open override /*2*/ fun foo(): jet.Unit
+}
+
+internal trait X {
+    internal abstract fun foo(): jet.Unit
+}
+
+internal trait Y : test.X {
+    internal abstract override /*1*/ /*fake_override*/ fun foo(): jet.Unit
+}