Make TASTy printer show tags in the binary format

This is to make it more robust in case there is an invalid/unhandled tag.

compiler/src/dotty/tools/dotc/core/tasty/AttributeUnpickler.scala

@@ -10,15 +10,18 @@ import java.nio.charset.StandardCharsets
 class AttributeUnpickler(reader: TastyReader):
   import reader._
 
-  lazy val attributes = {
+  lazy val attributeTags: List[Int] =
+    val listBuilder = List.newBuilder[Int]
+    while !isAtEnd do listBuilder += readNat()
+    listBuilder.result()
+
+  lazy val attributes: Attributes = {
     var scala2StandardLibrary = false
-    while (!isAtEnd) {
-      readNat() match
-        case TastyFormat.SCALA2STANDARDLIBRARYattr =>
-          scala2StandardLibrary = true
+    for attributeTag <- attributeTags do
+      attributeTag match
+        case TastyFormat.SCALA2STANDARDLIBRARYattr => scala2StandardLibrary = true
         case attribute =>
           assert(false, "Unexpected attribute value: " + attribute)
-    }
     Attributes(
       scala2StandardLibrary,
     )

compiler/src/dotty/tools/dotc/core/tasty/TastyPrinter.scala

@@ -225,15 +225,15 @@ class TastyPrinter(bytes: Array[Byte]) {
   }
 
   class AttributesSectionUnpickler extends SectionUnpickler[String](AttributesSection) {
-
+  import dotty.tools.tasty.TastyFormat.attributeTagToString
     private val sb: StringBuilder = new StringBuilder
 
     def unpickle(reader: TastyReader, tastyName: NameTable): String = {
       sb.append(s" ${reader.endAddr.index - reader.currentAddr.index}")
-      val attributes = new AttributeUnpickler(reader).attributes
+      val attributeTags = new AttributeUnpickler(reader).attributeTags
       sb.append(s"  attributes bytes:\n")
-      if attributes.scala2StandardLibrary then
-        sb.append("    SCALA2STANDARDLIBRARYattr\n")
+      for attributeTag <- attributeTags do
+        sb.append("    ").append(attributeTagToString(attributeTag)).append("\n")
       sb.result
     }
   }

tasty/src/dotty/tools/tasty/TastyFormat.scala

@@ -824,6 +824,10 @@ object TastyFormat {
     case HOLE => "HOLE"
   }
 
+  def attributeTagToString(tag: Int): String = tag match {
+    case SCALA2STANDARDLIBRARYattr => "SCALA2STANDARDLIBRARYattr"
+  }
+
   /** @return If non-negative, the number of leading references (represented as nats) of a length/trees entry.
    *          If negative, minus the number of leading non-reference trees.
    */