[Infra] move to netcoreapp 3.0

Author: reegeek

Build/Common.Benchmark.props

@@ -1,15 +1,15 @@
 <Project>
   <PropertyGroup Label="Framework">
-    <DefaultTargetFrameworks>netcoreapp2.1;net461</DefaultTargetFrameworks>
+    <DefaultTargetFrameworks>netcoreapp3.0;net461</DefaultTargetFrameworks>
   </PropertyGroup>
 
   <PropertyGroup>
     <OutputType>Exe</OutputType>
   </PropertyGroup>
 
   <ItemGroup>
-    <PackageReference Include="BenchmarkDotNet" Version="0.11.4" />
-    <PackageReference Include="BenchmarkDotNet.Diagnostics.Windows" Version="0.11.4" />
+    <PackageReference Include="BenchmarkDotNet" Version="0.11.5" />
+    <PackageReference Include="BenchmarkDotNet.Diagnostics.Windows" Version="0.11.5" />
   </ItemGroup>
 
   <Import Project="$(RootDir)\Build\DeleteGenerateBindingRedirects.target"/>

Build/Common.Tests.props

@@ -1,6 +1,6 @@
 <Project>
   <PropertyGroup Label="Framework">
-    <DefaultTargetFrameworks>netcoreapp2.0;net461</DefaultTargetFrameworks>
+    <DefaultTargetFrameworks>netcoreapp3.0;net461</DefaultTargetFrameworks>
   </PropertyGroup>
 
   <ItemGroup>

Build/Common.props

@@ -15,7 +15,7 @@
   </PropertyGroup>
 
   <PropertyGroup Label="Common properties">
-    <LangVersion>latest</LangVersion>
+    <LangVersion>8.0</LangVersion>
   </PropertyGroup>