Fix for KT-10881 Declaring constant in a mutlifile class causes an IllegalAccessError on its usage.

Generate fields for 'const' properties in facade class.

NB reading annotations for 'const' vals in multifile class doesn't work, KT-10892.

compiler/testData/codegen/boxMultifileClasses/calls/constFromOtherPackage.1.kt

@@ -0,0 +1,3 @@
+import a.OK
+
+fun box(): String = OK

compiler/testData/codegen/boxMultifileClasses/calls/constFromOtherPackage.2.kt

@@ -0,0 +1,4 @@
+@file:[JvmName("MultifileClass") JvmMultifileClass]
+package a
+
+const val OK: String = "OK"