Subclasses of this component can customize it by wrapping with the
decorator pattern, and a custom `CompositeSequencableLoaderFactory`
allows access to the list of delegate `SequenceableLoader` instances.
The `final` keyword was removed as part of <unknown commit> but this
component never ended up being subclassed within the library.
Making this class `final` makes upcoming changes easier to reason
about.
PiperOrigin-RevId: 597853429
d4be30b04d