Use `.dotnet` instead of `.net` for single file applications in .NET 7

See: https://github.com/dotnet/runtime/issues/35221#issuecomment-909595319

Single file apps extract to `$HOME/.net`, instead of using on one of the already-common directories like `$HOME/.dotnet` or even `$XDG_CACHE_HOME` (with fallback to `$HOME/.cache`).

For .NET 7, we should try and fix this and use `$HOME/.dotnet` instead of adding one more dot-directory to the user's home.