Enable implicit namespaces and clean up usings (#1497)

Author: JamesNK

Directory.Build.props

@@ -20,6 +20,7 @@
     <EmbedUntrackedSources>true</EmbedUntrackedSources>
     <LangVersion>10.0</LangVersion>
     <Nullable>enable</Nullable>
+    <ImplicitUsings>enable</ImplicitUsings>
   </PropertyGroup>
 
 </Project>

perf/Grpc.AspNetCore.Microbenchmarks/Client/CompressedUnaryClientBenchmark.cs

@@ -16,9 +16,6 @@
 
 #endregion
 
-using System.Collections.Generic;
-using System.IO;
-using System.Threading.Tasks;
 using BenchmarkDotNet.Attributes;
 using Greet;
 using Grpc.AspNetCore.Microbenchmarks.Internal;

perf/Grpc.AspNetCore.Microbenchmarks/Client/UnaryClientBenchmark.cs

@@ -16,7 +16,6 @@
 
 #endregion
 
-using System.Threading.Tasks;
 using BenchmarkDotNet.Attributes;
 using Grpc.Core;
 

perf/Grpc.AspNetCore.Microbenchmarks/Client/UnaryClientBenchmarkBase.cs

@@ -16,14 +16,8 @@
 
 #endregion
 
-using System;
-using System.Collections.Generic;
-using System.IO;
-using System.Linq;
 using System.Net;
-using System.Net.Http;
 using System.Net.Http.Headers;
-using System.Threading.Tasks;
 using BenchmarkDotNet.Attributes;
 using Greet;
 using Grpc.AspNetCore.Microbenchmarks.Internal;

perf/Grpc.AspNetCore.Microbenchmarks/DefaultCoreConfigAttribute.cs

@@ -16,7 +16,6 @@
 
 #endregion
 
-using System;
 using BenchmarkDotNet.Configs;
 
 namespace Grpc.AspNetCore.Microbenchmarks

perf/Grpc.AspNetCore.Microbenchmarks/Internal/ForceAsyncAwaiter.cs

@@ -16,9 +16,7 @@
 
 #endregion
 
-using System;
 using System.Runtime.CompilerServices;
-using System.Threading.Tasks;
 
 namespace Grpc.AspNetCore.Microbenchmarks.Internal
 {

perf/Grpc.AspNetCore.Microbenchmarks/Internal/MessageHelpers.cs

@@ -16,7 +16,6 @@
 
 #endregion
 
-using System.IO;
 using System.IO.Pipelines;
 using Google.Protobuf;
 using Grpc.AspNetCore.Server.Internal;

perf/Grpc.AspNetCore.Microbenchmarks/Internal/TestCompressionProvider.cs

@@ -16,7 +16,6 @@
 
 #endregion
 
-using System.IO;
 using System.IO.Compression;
 using Grpc.Net.Compression;
 

perf/Grpc.AspNetCore.Microbenchmarks/Internal/TestGrpcInterceptorActivator.cs

@@ -16,10 +16,7 @@
 
 #endregion
 
-using System;
-using System.Threading.Tasks;
 using Grpc.AspNetCore.Server;
-using Grpc.AspNetCore.Server.Internal;
 using Grpc.Core.Interceptors;
 
 namespace Grpc.AspNetCore.Microbenchmarks.Internal

perf/Grpc.AspNetCore.Microbenchmarks/Internal/TestGrpcServiceActivator.cs

@@ -16,8 +16,6 @@
 
 #endregion
 
-using System;
-using System.Threading.Tasks;
 using Grpc.AspNetCore.Server;
 
 namespace Grpc.AspNetCore.Microbenchmarks.Internal