[test] Update api-digester source compatibility tests

DictionaryIterator & SetIterator have been renamed Dictionary.Iterator and Set.Iterator, with compatibility typealiases.

Author: lorentey

stdlib/public/core/Dictionary.swift

@@ -572,7 +572,7 @@ extension Dictionary: Sequence {
   ///   `(key: Key, value: Value)`.
   @inlinable
   @inline(__always)
-  public func makeIterator() -> Dictionary<Key, Value>.Iterator {
+  public func makeIterator() -> Iterator {
     return _variant.makeIterator()
   }
 }

stdlib/public/core/Set.swift

@@ -233,7 +233,7 @@ extension Set: Sequence {
   /// Returns an iterator over the members of the set.
   @inlinable
   @inline(__always)
-  public func makeIterator() -> Set<Element>.Iterator {
+  public func makeIterator() -> Iterator {
     return _variant.makeIterator()
   }
 

test/api-digester/source-stability.swift.expected

@@ -0,0 +1,15 @@
+/* FIXME: Bogus */
+TypeAlias DictionaryIterator.Element has been removed
+TypeAlias SetIterator.Element has been removed
+Var DictionaryIterator.customMirror has been removed
+Var SetIterator.customMirror has been removed
+Func DictionaryIterator.next() has been removed
+Func SetIterator.next() has been removed
+
+/* Renamed Decls (FIXME: Targets are Dictionary.Iterator & Set.Iterator) */
+Struct DictionaryIterator has been renamed to Struct Iterator
+Struct SetIterator has been renamed to Struct Iterator
+
+/* FIXME: Bogus */
+Func Dictionary.makeIterator() has return type change from DictionaryIterator<Dictionary<Key, Value>.Key, Dictionary<Key, Value>.Value> to Dictionary<Key, Value>.Iterator
+Func Set.makeIterator() has return type change from SetIterator<Element> to Set<Element>.Iterator