[Improvement] generate bundle_name in `syndicate assemble` command if not provided

[bohdan-onsha]

Add ability to generate bundle_name in syndicate assemble command if not provided.

Just need to change bundle_name attribute callback to generate_default_bundle_name (used by syndicate build)

[dmytro-afanasiev]

These changes were made in Thursday but I seem to forget to make a pull request. Here it is.