[infra] Translate _sources.gypi files to _sources.gni files

sdk/lib/convert/convert_sources.gypi

Index: sdk/lib/convert/convert_sources.gypi
diff --git a/sdk/lib/convert/convert_sources.gypi b/sdk/lib/convert/convert_sources.gypi
deleted file mode 100644
index d8d40cb68a4db0746e4abc35f0bad85d40930136..0000000000000000000000000000000000000000
--- a/sdk/lib/convert/convert_sources.gypi
+++ /dev/null
@@ -1,24 +0,0 @@
-# Copyright (c) 2013, the Dart project authors.  Please see the AUTHORS file
-# for details. All rights reserved. Use of this source code is governed by a
-# BSD-style license that can be found in the LICENSE file.
-
-# This file contains all sources for the dart:convert library.
-{
-  'sources': [
-    'convert.dart',
-    # The above file needs to be first as it lists the parts below.
-    'ascii.dart',
-    'base64.dart',
-    'byte_conversion.dart',
-    'chunked_conversion.dart',
-    'codec.dart',
-    'converter.dart',
-    'encoding.dart',
-    'html_escape.dart',
-    'json.dart',
-    'latin1.dart',
-    'line_splitter.dart',
-    'string_conversion.dart',
-    'utf.dart',
-  ],
-}