Refactor end2end_test. Make the credentials a separate library.
diff --git a/tools/run_tests/sources_and_headers.json b/tools/run_tests/sources_and_headers.json
index 5b1b674..80edd6d 100644
--- a/tools/run_tests/sources_and_headers.json
+++ b/tools/run_tests/sources_and_headers.json
@@ -4186,7 +4186,8 @@
       "test/cpp/util/cli_call.h", 
       "test/cpp/util/create_test_channel.h", 
       "test/cpp/util/string_ref_helper.h", 
-      "test/cpp/util/subprocess.h"
+      "test/cpp/util/subprocess.h", 
+      "test/cpp/util/test_credentials_provider.h"
     ], 
     "language": "c++", 
     "name": "grpc++_test_util", 
@@ -4202,7 +4203,9 @@
       "test/cpp/util/string_ref_helper.cc", 
       "test/cpp/util/string_ref_helper.h", 
       "test/cpp/util/subprocess.cc", 
-      "test/cpp/util/subprocess.h"
+      "test/cpp/util/subprocess.h", 
+      "test/cpp/util/test_credentials_provider.cc", 
+      "test/cpp/util/test_credentials_provider.h"
     ]
   }, 
   {