Compile using ref assemblies (dotnet/extensions#2483)

* Compile using ref assemblies

* Use updated ResolveReferences.target from AspNetCore

* Generate ref assemblies for .NET framework\n\nCommit migrated from dotnet/extensions@e771c42

Author: John Luo

src/Shared/src/ProviderAliasUtilities/ProviderAliasUtilities.cs

@@ -0,0 +1,34 @@
+// Copyright (c) .NET Foundation. All rights reserved.
+// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
+
+using System;
+using System.Reflection;
+
+namespace Microsoft.Extensions.Logging
+{
+    internal static class ProviderAliasUtilities
+    {
+        private const string AliasAttibuteTypeFullName = "Microsoft.Extensions.Logging.ProviderAliasAttribute";
+        private const string AliasAttibuteAliasProperty = "Alias";
+
+        internal static string GetAlias(Type providerType)
+        {
+            foreach (var attribute in providerType.GetTypeInfo().GetCustomAttributes(inherit: false))
+            {
+                if (attribute.GetType().FullName == AliasAttibuteTypeFullName)
+                {
+                    var valueProperty = attribute
+                        .GetType()
+                        .GetProperty(AliasAttibuteAliasProperty, BindingFlags.Public | BindingFlags.Instance);
+
+                    if (valueProperty != null)
+                    {
+                        return valueProperty.GetValue(attribute) as string;
+                    }
+                }
+            }
+
+            return null;
+        }
+    }
+}

src/TestingUtils/Microsoft.AspNetCore.Testing/ref/Microsoft.AspNetCore.Testing.csproj

@@ -0,0 +1,32 @@
+<!-- This file is automatically generated. -->
+<Project Sdk="Microsoft.NET.Sdk">
+  <PropertyGroup>
+    <TargetFrameworks>netstandard2.0;net46</TargetFrameworks>
+  </PropertyGroup>
+  <ItemGroup Condition="'$(TargetFramework)' == 'netstandard2.0'">
+    <Compile Include="Microsoft.AspNetCore.Testing.netstandard2.0.cs" />
+    <Reference Include="Microsoft.Win32.Registry"  />
+    <Reference Include="System.ValueTuple"  />
+    <Reference Include="xunit.assert"  />
+    <Reference Include="xunit.extensibility.execution"  />
+  </ItemGroup>
+<ItemGroup Condition="'$(TargetFramework)' == 'net46'">
+    <Compile Include="Microsoft.AspNetCore.Testing.net46.cs" />
+    <Reference Include="Microsoft.Win32.Registry"  />
+    <Reference Include="System.ValueTuple"  />
+    <Reference Include="xunit.assert"  />
+    <Reference Include="xunit.extensibility.execution"  />
+    <Reference Include="System.Net.Http"  />
+    <Reference Include="System.Runtime.InteropServices.RuntimeInformation"  />
+    <Reference Include="System"  />
+    <Reference Include="System.Data"  />
+    <Reference Include="System.Drawing"  />
+    <Reference Include="System.Xml"  />
+    <Reference Include="System.Core"  />
+    <Reference Include="System.Runtime.Serialization"  />
+    <Reference Include="System.Xml.Linq"  />
+    <Reference Include="System.Numerics"  />
+    <Reference Include="System.IO.Compression.FileSystem"  />
+    <Reference Include="mscorlib"  />
+  </ItemGroup>
+</Project>