Add back ScalaValueClasses() initialization

The call to `apply` perform side effects that need to be executed

[Cherry-picked 240e95a]

Author: lolgab

Diff for: compiler/src/dotty/tools/dotc/core/Definitions.scala

@@ -2132,6 +2132,7 @@ class Definitions {
       // force initialization of every symbol that is synthesized or hijacked by the compiler
       syntheticCoreClasses
       syntheticCoreMethods
+      ScalaValueClasses()
       JavaEnumClass
       // end force initialization
       isInitialized = true