refactor: remove legacy equatable code

lib/src/_data_class.dart

@@ -6,41 +6,3 @@ final dataClassMacro = Uri.parse('package:data_class/src/_data_class.dart');
 
 // Methods used in augmented code.
 const undefined = Object();
-final deepEquals = const DeepCollectionEquality().equals;
-
-// TODO(felangel): use jenkins hash from `package:equatable`
-// once https://github.com/felangel/equatable/pull/174 is published.
-/// Generate a hash for the provided [fields].
-int hashAll(Iterable<Object?>? fields) {
-  return _finish(fields == null ? 0 : fields.fold(0, _combine));
-}
-
-int _combine(int hash, Object? object) {
-  if (object is Map) {
-    object.keys
-        .sorted((Object? a, Object? b) => a.hashCode - b.hashCode)
-        .forEach((Object? key) {
-      hash = hash ^ _combine(hash, [key, (object! as Map)[key]]);
-    });
-    return hash;
-  }
-  if (object is Set) {
-    object = object.sorted((Object? a, Object? b) => a.hashCode - b.hashCode);
-  }
-  if (object is Iterable) {
-    for (final value in object) {
-      hash = hash ^ _combine(hash, value);
-    }
-    return hash ^ object.length;
-  }
-
-  hash = 0x1fffffff & (hash + object.hashCode);
-  hash = 0x1fffffff & (hash + ((0x0007ffff & hash) << 10));
-  return hash ^ (hash >> 6);
-}
-
-int _finish(int hash) {
-  hash = 0x1fffffff & (hash + ((0x03ffffff & hash) << 3));
-  hash = hash ^ (hash >> 11);
-  return 0x1fffffff & (hash + ((0x00003fff & hash) << 15));
-}