Log pid of remote executed process. (#5525)

When debugging different parts of the test pipeline it is good to see
the different pids of launched processes in case there is need to attach
debugger to it. For the debuggee we output the pid, but for the debugger
executed through remote executor we didn't. This PR adds logging to
output pid of started process.

Author: lateralusX

src/Microsoft.Diagnostics.TestHelpers/RemoteExecutorHelper.cs

@@ -29,6 +29,9 @@ public static async Task<int> RemoteInvoke(ITestOutputHelper output, TestConfigu
             // When RemoteExecutor is fixed the "using" can be added and the GC.SuppressFinalize be removed.
             RemoteInvokeHandle remoteInvokeHandle = RemoteExecutor.Invoke(method, config.Serialize(), options);
             GC.SuppressFinalize(remoteInvokeHandle);
+
+            output.WriteLine($"RemoteExecutorHelper.RemoteInvoke: starting process {remoteInvokeHandle.Process.Id}");
+
             try
             {
                 Task stdOutputTask = WriteStreamToOutput(remoteInvokeHandle.Process.StandardOutput, output);