Fix MonoCrossAOT.UnixFilePermissions for wasm (#54693)

Fix MonoCrossAOT.UnixFilePermissions for wasm (#54693)

* Fix MonoCrossAOT.UnixFilePermissions for wasm

We introduced Microsoft.NETCore.App.MonoCrossAOT.UnixFilePermissions.xml in https://github.com/dotnet/runtime/pull/54501 to make sure the right permissions are set when installing AOT compiler workload packs.  We hardcoded the list to include mono-aot-cross, llc, and opt.  However, in wasm's case they only have mono-aot-cross.

This change makes the xml file a template and only includes mono-aot-cross for browser and all three for the other configurations.

Fixes https://github.com/dotnet/runtime/issues/54612

* Use property instead of item for the file nodes

* Ankit suggestion

Co-authored-by: Steve Pfister <steve.pfister@microsoft.com>