SI-8024 Improve user-level toString of package objects

We were outputing a the unattractive `package package`;
now we opt for `package object pack`.

Under `-Ydebug`, we still go to the "accurate" mode of the
old `toString` implementation, which differentiates package objects
vs package object classes.

src/reflect/scala/reflect/internal/Symbols.scala

@@ -2475,10 +2475,14 @@ trait Symbols extends api.Symbols { self: SymbolTable =>
     /** String representation, including symbol's kind e.g., "class Foo", "method Bar".
      *  If hasMeaninglessName is true, uses the owner's name to disambiguate identity.
      */
-    override def toString: String = compose(
-      kindString,
-      if (hasMeaninglessName) owner.decodedName + idString else nameString
-    )
+    override def toString: String = {
+      if (isPackageObjectOrClass && !settings.debug)
+        s"package object ${owner.decodedName}"
+      else compose(
+        kindString,
+        if (hasMeaninglessName) owner.decodedName + idString else nameString
+      )
+    }
 
     /** String representation of location.
      */

test/files/neg/t8024.check

@@ -1,5 +1,5 @@
 t8024.scala:13: error: reference to sqrt is ambiguous;
-it is both defined in package package and imported subsequently by
+it is both defined in package object p and imported subsequently by
 import java.lang.Math.sqrt
   sqrt(0d)
   ^