Pass deps collection to be expanded as a parameter
Use separate collection for requirement deps
Move dependency expansion logic up one level
Rename filter_deps to expand_dependencies
Compute recursive deps for default_formula deps
Ensure option names are consistent for default formula requirements
Expand requirements of default deps added by other requirements

Dependencies built from requirements with a default formula may
themselves have requirements, and these requirements may have default
formulae, which may have more requirements, etc., so we have to keep
expanding until this isn't the case.