GN: Build rules and fixes for (almost) all mojo unittest targets

mojo/public/cpp/test_support/BUILD.gn

 # Copyright 2014 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
-source_set("auto_login_parser") {
-  sources = [
-    "auto_login_parser.cc",
-    "auto_login_parser.h",
+# GYP version: mojo/mojo_public_tests.gypi:mojo_public_test_utils
+source_set("test_utils") {
+  deps = [
+    "//base",
+    "//testing/gtest",
+    "//mojo/public/c/test_support",
   ]
 
-  deps = [
-    "//base",
-    "//net",
+  sources = [
+    "lib/test_support.cc",
+    "lib/test_utils.cc",
+    "test_utils.h",
   ]
 }
-
-source_set("unit_tests") {
-  sources = [
-    "auto_login_parser_unittest.cc",
-  ]
-
-  deps = [
-    ":auto_login_parser",
-    "//testing/gtest",
-  ]
-}