dotnetCorePackages.dotnet_{8..10}.packages: init as recursed set

These packages are exposed in the sdk via passthru.packages, but aren't
in the binary cache.  This makes them reachable.

pkgs/development/compilers/dotnet/packages.nix

@@ -249,4 +249,8 @@ in
     aspnetcore
     ;
 
+  packages = lib.recurseIntoAttrs (
+    # recursion can't handle . in the attribute names
+    lib.genAttrs' packages (p: lib.nameValuePair (lib.replaceString "." "-" p.pname) p)
+  );
 }