[release/8.0] Readd DiagnosticSource to KestrelServerImpl#60203

wtgodbe merged 2 commits intorelease/8.0dotnet/aspnetcore:release/8.0from

backport/pr-60129-to-release/8.0dotnet/aspnetcore:backport/pr-60129-to-release/8.0Copy head branch name to clipboard