Add error for sql bindings when .net 5 (#1259)

* add error for sql bindings when .net 5

* add test

* cleanup linq stuff and move out common code

test/Microsoft.SqlTools.ServiceLayer.IntegrationTests/AzureFunctions/AzureFunctionTestFiles/AzureFunctionsNet5.cs

@@ -0,0 +1,26 @@
+using System.Collections.Generic;
+using System.Net;
+using Microsoft.Azure.Functions.Worker;
+using Microsoft.Azure.Functions.Worker.Http;
+using Microsoft.Extensions.Logging;
+
+namespace Company.Function
+{
+    public static class HttpTrigger1
+    {
+        [Function("HttpTrigger1")]
+        public static HttpResponseData Run([HttpTrigger(AuthorizationLevel.Anonymous, "get", "post")] HttpRequestData req,
+            FunctionContext executionContext)
+        {
+            var logger = executionContext.GetLogger("HttpTrigger1");
+            logger.LogInformation("C# HTTP trigger function processed a request.");
+
+            var response = req.CreateResponse(HttpStatusCode.OK);
+            response.Headers.Add("Content-Type", "text/plain; charset=utf-8");
+
+            response.WriteString("Welcome to Azure Functions!");
+
+            return response;
+        }
+    }
+}