Report error on state in multi-file class with -Xmultifile-parts-inherit

Simplify MultifileClassPartCodegen, remove related tests and change some
tests to use const val instead of val because backing fields for const
properties are stored in the facade, not parts

 #KT-23701 Fixed

compiler/testData/codegen/box/multifileClasses/optimized/callableRefToConstVal.kt

@@ -0,0 +1,16 @@
+// IGNORE_BACKEND: JVM_IR
+// TARGET_BACKEND: JVM
+// IGNORE_LIGHT_ANALYSIS
+// WITH_RUNTIME
+// !INHERIT_MULTIFILE_PARTS
+// FILE: box.kt
+
+import a.*
+
+fun box(): String = ::OK.get()
+
+// FILE: part1.kt
+@file:[JvmName("MultifileClass") JvmMultifileClass]
+package a
+
+const val OK = "OK"