Postpone companion object field visibility

Have to reconsider this issue because of interface companion objects.

compiler/testData/codegen/bytecodeListing/companionObjectVisibility_lv13.kt

@@ -0,0 +1,17 @@
+// LANGUAGE_VERSION: 1.3
+
+open class TestProtectedCompanionInClass {
+    protected companion object
+}
+
+class TestInternalCompanionInClass {
+    internal companion object
+}
+
+class TestPrivateCompanionInClass {
+    private companion object
+}
+
+interface TestPrivateCompanionInInterface {
+    private companion object
+}