Workaround more precise type patterns in scalac: scala/scala3#3208

Author: allanrenucci

scalatest/src/main/scala/org/scalatest/AppendedClues.scala

@@ -158,7 +158,7 @@ trait AppendedClues {
         }
       }
       catch {
-        case e: ModifiableMessage[_] =>
+        case e: ModifiableMessage[_] with Throwable =>
           if (clue.toString != "")
             throw e.modifyMessage(append)
           else

scalatest/src/main/scala/org/scalatest/Assertions.scala

@@ -1171,7 +1171,7 @@ trait Assertions extends TripleEquals  {
       }
     }
     catch {
-      case e: org.scalatest.exceptions.ModifiableMessage[_] =>
+      case e: org.scalatest.exceptions.ModifiableMessage[_] with Throwable =>
         if (clue != "")
           throw e.modifyMessage(prepend)
         else

scalatest/src/main/scala/org/scalatest/Checkpoints.scala

@@ -136,7 +136,7 @@ trait Checkpoints {
         case e: TestRegistrationClosedException => throw e
         case e: NotAllowedException => throw e
         case e: DuplicateTestNameException => throw e
-        case e: StackDepth  => failures.add(e)
+        case e: StackDepth with Throwable => failures.add(e)
         case e: Throwable => throw e
       }
     }