[WIP] Reduce test target complexity [and running time] (#5403)

* Reduce test target complexity [and running time]

* WiP

* Enable building tests via solution

Remove deprecated tests
Make Microsoft.DotNet.Tools.Tests.Utilities portable-only
Remove MSI tests from the solution as they are the only  tests that currently require dekstop.

* Enable building of tests

* Move migration tests to TA to allow them to self-restore

* Reduce project nesting and test directory name

TestAssets/TestProjects/ProjectsWithGlobalJson/src/ProjectH/Program.cs

@@ -0,0 +1,19 @@
+// 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.Diagnostics;
+
+namespace TestApp
+{
+    public class Program
+    {
+        public static int Main(string[] args)
+        {
+            Console.WriteLine("This string came from ProjectH");
+            string helperStr = TestLibrary.ProjectI.GetMessage();
+            Console.WriteLine(helperStr);
+            return 0;
+        }
+    }
+}

TestAssets/TestProjects/ProjectsWithGlobalJson/src/ProjectH/project.json

@@ -0,0 +1,20 @@
+{
+  "version": "1.0.0-*",
+  "buildOptions": {
+    "emitEntryPoint": true,
+    "preserveCompilationContext": true
+  },
+  "dependencies": {
+    "ProjectI": {
+      "target": "project",
+      "version": "1.0.0-*"
+    },
+    "Microsoft.NETCore.App": {
+      "type": "platform",
+      "version": "1.0.1"
+    }
+  },
+  "frameworks": {
+    "netcoreapp1.0": {}
+  }
+}

TestAssets/TestProjects/ProjectsWithGlobalJson/src/ProjectI/Helper.cs

@@ -0,0 +1,15 @@
+// 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;
+
+namespace TestLibrary
+{
+    public static class ProjectI
+    {
+        public static string GetMessage()
+        {
+            return "This string came from ProjectI";
+        }
+    }
+}

TestAssets/TestProjects/ProjectsWithGlobalJson/src/ProjectI/project.json

@@ -0,0 +1,18 @@
+{
+  "version": "1.0.0-*",
+  "buildOptions": {
+    "nowarn": [
+      "CS1591"
+    ],
+    "xmlDoc": true,
+    "additionalArguments": [
+      "-highentropyva+"
+    ]
+  },
+  "dependencies": {
+    "NETStandard.Library": "1.6.0"
+  },
+  "frameworks": {
+    "netstandard1.5": {}
+  }
+}