AnonymousLoader evaluates Ruby source files inside fresh anonymous modules. It
is useful when a tool needs to inspect or reuse code that declares constants
whose top-level names may collide with the host process.

The loaded source keeps its normal constant nesting, but that nesting starts
inside the returned anonymous namespace. For example, source that declares
Auth::Sanitizer becomes namespace::Auth::Sanitizer, and does not create
Object::Auth.

AnonymousLoader can load explicitly named files, or resolve a file using
RubyGems metadata with a $LOAD_PATH fallback. The fallback is intended for
Bundler standalone and similar environments where code is loadable but a gem is
not visible through Gem.loaded_specs or the normal RubyGems index.