add Tony Stone's 'process_test_files.rb' to NOTICE

and move "XCTest+AsyncAwait.swift" from gRPC Swift into its own section

Author: dnadoba

NOTICE.txt

@@ -24,20 +24,32 @@ Also, please refer to each LICENSE.txt file, which is located in
 the 'license' directory of the distribution file, for the license terms of the
 components that this product depends on.
 
--------------------------------------------------------------------------------
+---
 
-
-This product contains derivations of various scripts from SwiftNIO and contains "XCTest+AsyncAwait.swift" from gRPC Swift.
+This product contains derivations of various scripts from SwiftNIO.
 
   * LICENSE (Apache License 2.0):
     * https://www.apache.org/licenses/LICENSE-2.0
   * HOMEPAGE:
     * https://github.com/apple/swift-nio
 
+---
+    
+This product contains "XCTest+AsyncAwait.swift" from gRPC Swift.
+
   * LICENSE (Apache License 2.0):
     * https://www.apache.org/licenses/LICENSE-2.0
   * HOMEPAGE:
     * https://github.com/grpc/grpc-swift
 
+---
+
+This product contains a derivation of the Tony Stone's 'process_test_files.rb'.
+
+  * LICENSE (Apache License 2.0):
+    * https://www.apache.org/licenses/LICENSE-2.0
+  * HOMEPAGE:
+    * https://github.com/tonystone/build-tools/commit/6c417b7569df24597a48a9aa7b505b636e8f73a1
+    * https://github.com/tonystone/build-tools/blob/master/source/xctest_tool.rb
 
--------------------------------------------------------------------------------
+---