fix: make the order of the keys in the Map deterministic

This was introduced in #23769 but it makes the following test fail: https://github.com/scala/scala3/blob/48bc891bd317a62956dc86297feb6e86a73083f6/tests/run/t4954.scala#L8

Author: hamzaremmal

library/src/scala/collection/Map.scala

@@ -216,7 +216,7 @@ transparent trait MapOps[K, +V, +CC[_, _] <: IterableOps[_, AnyConstr, _], +C]
     */
   protected trait GenKeySet { this: Set[K] =>
     // CC note: this is unavoidable to make the KeySet pure.
-    private[MapOps] val allKeys = MapOps.this.keysIterator.toSet
+    private[MapOps] val allKeys = MapOps.this.keysIterator.toList
     // We restore the lazy behavior in LazyKeySet
     def iterator: Iterator[K] =
       allKeys.iterator