Add toString() to Any, fix all tests

#KT-4517 Fixed

compiler/testData/codegen/box/traits/kt2399.kt

@@ -7,7 +7,7 @@ class JsonArray {
 }
 
 class ProjectInfo {
-    public fun toString(): String = "OK"
+    override fun toString(): String = "OK"
 }
 
 public trait Parser<in IN: Any, out OUT: Any> {

compiler/testData/codegen/box/traits/withRequiredPropertyViaBridge.kt

@@ -4,7 +4,7 @@ trait Trait : Base {
     private val value : String
         get() = "OK"
         
-    fun toString() = object {
+    override fun toString() = object {
         fun foo() = value
     }.foo()
 }