Don't use reflection to call Iterable.collectionClassName

This is an issue on GraalVM, where all collection concrete classes would
need to be added to some Graal reflection config for collectionClassName
to be call-able by reflection.

Author: alexarchambault

pprint/src-2.13/pprint/StringPrefix.scala

@@ -1,5 +1,6 @@
 package pprint
 
 object StringPrefix{
-  def apply(i: Iterable[_]) = i.asInstanceOf[{ def collectionClassName: String }].collectionClassName
+  def apply(i: Iterable[_]) =
+    scala.collection.internal.pprint.CollectionName.get(i)
 }

pprint/src-2.13/scala/collection/internal/pprint/CollectionName.scala

@@ -0,0 +1,6 @@
+package scala.collection.internal.pprint
+
+object CollectionName {
+  def get(iterable: scala.collection.Iterable[_]): String =
+    iterable.collectionClassName
+}

pprint/src-3/StringPrefix.scala

@@ -1,7 +1,6 @@
 package pprint
 
-import reflect.Selectable.reflectiveSelectable
-
 object StringPrefix{
-  def apply(i: Iterable[_]) = i.asInstanceOf[{ def collectionClassName: String }].collectionClassName
+  def apply(i: Iterable[_]) =
+    scala.collection.internal.pprint.CollectionName.get(i)
 }

pprint/src-3/scala/collection/internal/pprint/CollectionName.scala

@@ -0,0 +1,6 @@
+package scala.collection.internal.pprint
+
+object CollectionName {
+  def get(iterable: scala.collection.Iterable[_]): String =
+    iterable.collectionClassName
+}