java intrinsics: change array_get from intrinsic_constructor to ins…

[michaellilltokiwa]

…trinsic

this fixes "Used abstract feature.." in javabase test:

  # NYI does not work yet: error 1: Used abstract feature 'String.utf8' is not implemented by 'String'
  # say (fuzion.java.array_to_java_object ["1","2","3"])

but now a new error:
java.lang.ClassCastException: class fzC_Const_String cannot be cast to class fzC_String (fzC_Const_String and fzC_String are in unnamed module of loader dev.flang.be.jvm.Runner @658c5a19)

[fridis]

java.lang.ClassCastException: class fzC_Const_String cannot be cast to class fzC_String

This should probably cast to fzI_String, fzC_String should only be used if the JVM backend is sure that there are no instantiated child features of fzC_String. So the code that decides if the need an interface or only a class depending on the children does not work as expected here.