Console.Write() doesn't show output until a newline

When running an app with `dotnet run`, we are redirecting the standard out and error just to print it out to our standard out and error. However, we are batching the output until we hit a newline, which isn't ideal for console apps.

To fix this, `dotnet run` no longer redirects the standard out and error.

Fix #2777

test/dotnet-run.UnitTests/GivenARunCommand.cs

@@ -0,0 +1,122 @@
+// Copyright (c) .NET Foundation and contributors. All rights reserved.
+// Licensed under the MIT license. See LICENSE file in the project root for full license information.
+
+using System;
+using System.Collections.Generic;
+using System.IO;
+using FluentAssertions;
+using Microsoft.DotNet.Cli.Utils;
+using Microsoft.DotNet.TestFramework;
+using Microsoft.DotNet.Tools.Test.Utilities;
+using NuGet.Frameworks;
+using Xunit;
+
+namespace Microsoft.DotNet.Tools.Run.Tests
+{
+    public class GivenARunCommand : TestBase
+    {
+        private const int RunExitCode = 29;
+
+        [Fact]
+        public void ItDoesntRedirectStandardOutAndError()
+        {
+            TestInstance instance = TestAssetsManager.CreateTestInstance("TestAppSimple")
+                                         .WithLockFiles();
+
+            new BuildCommand(instance.TestRoot)
+                .Execute()
+                .Should()
+                .Pass();
+
+            RunCommand runCommand = new RunCommand(new FailOnRedirectOutputCommandFactory());
+            runCommand.Project = instance.TestRoot;
+
+            runCommand.Start()
+                .Should()
+                .Be(RunExitCode);
+        }
+
+        private class FailOnRedirectOutputCommandFactory : ICommandFactory
+        {
+            public ICommand Create(string commandName, IEnumerable<string> args, NuGetFramework framework = null, string configuration = "Debug")
+            {
+                return new FailOnRedirectOutputCommand();
+            }
+
+            /// <summary>
+            /// A Command that will fail if a caller tries redirecting StdOut or StdErr.
+            /// </summary>
+            private class FailOnRedirectOutputCommand : ICommand
+            {
+                public CommandResult Execute()
+                {
+                    return new CommandResult(null, RunExitCode, null, null);
+                }
+
+                public ICommand CaptureStdErr()
+                {
+                    throw new NotSupportedException();
+                }
+
+                public ICommand CaptureStdOut()
+                {
+                    throw new NotSupportedException();
+                }
+
+                public ICommand ForwardStdErr(TextWriter to = null, bool onlyIfVerbose = false, bool ansiPassThrough = true)
+                {
+                    throw new NotSupportedException();
+                }
+
+                public ICommand ForwardStdOut(TextWriter to = null, bool onlyIfVerbose = false, bool ansiPassThrough = true)
+                {
+                    throw new NotSupportedException();
+                }
+
+                public ICommand OnErrorLine(Action<string> handler)
+                {
+                    throw new NotSupportedException();
+                }
+
+                public ICommand OnOutputLine(Action<string> handler)
+                {
+                    throw new NotSupportedException();
+                }
+
+                public string CommandArgs
+                {
+                    get
+                    {
+                        throw new NotImplementedException();
+                    }
+                }
+
+                public string CommandName
+                {
+                    get
+                    {
+                        throw new NotImplementedException();
+                    }
+                }
+
+                public CommandResolutionStrategy ResolutionStrategy
+                {
+                    get
+                    {
+                        throw new NotImplementedException();
+                    }
+                }
+
+                public ICommand EnvironmentVariable(string name, string value)
+                {
+                    throw new NotImplementedException();
+                }
+
+                public ICommand WorkingDirectory(string projectDirectory)
+                {
+                    throw new NotImplementedException();
+                }
+            }
+        }
+    }
+}