Expand EOL list to include net7 6 months after it goes OOS per design

Author: marcpopMSFT

src/Tasks/Microsoft.NET.Build.Tasks/targets/Microsoft.NET.EolTargetFrameworks.targets

@@ -21,7 +21,7 @@ Copyright (c) .NET Foundation. All rights reserved.
     receive servicing updates and security fixes.
   -->
   <ItemGroup>
-    <_EolNetCoreTargetFrameworkVersions Include="1.0;1.1;2.0;2.1;2.2;3.0;3.1;5.0" />
+    <_EolNetCoreTargetFrameworkVersions Include="1.0;1.1;2.0;2.1;2.2;3.0;3.1;5.0;7.0" />
   </ItemGroup>
   <PropertyGroup>
     <_MinimumNonEolSupportedNetCoreTargetFramework>net6.0</_MinimumNonEolSupportedNetCoreTargetFramework>

test/Microsoft.NET.Build.Tests/GivenThatWeWantToTargetEolFrameworks.cs

@@ -15,6 +15,7 @@ public GivenThatWeWantToTargetEolFrameworks(ITestOutputHelper log) : base(log)
         [InlineData("netcoreapp3.0")]
         [InlineData("netcoreapp3.1")]
         [InlineData("net5.0")]
+        [InlineData("net7.0")]
         public void It_warns_that_framework_is_out_of_support(string targetFrameworks)
         {
             var testProject = new TestProject()