Reorganize code so Kestrel now produces the Microsoft.Extensions.Buffers.Testing.Sources package

NuGetPackageVerifier.json

@@ -1,7 +1,13 @@
 {
+    "adx-nonshipping": {
+        "rules": [],
+        "packages": {
+            "Microsoft.Extensions.Buffers.Testing.Sources": {}
+        }
+    },
     "Default": {
         "rules": [
             "DefaultCompositeRule"
         ]
     }
-}
+}

test/Kestrel.Core.Tests/Kestrel.Core.Tests.csproj

@@ -9,6 +9,7 @@
 
   <ItemGroup>
     <Compile Include="..\shared\**\*.cs" />
+    <Compile Include="..\..\shared\Microsoft.Extensions.Buffers.Testing.Sources\*.cs" />
     <Content Include="..\shared\TestCertificates\*.pfx" CopyToOutputDirectory="PreserveNewest" />
   </ItemGroup>