In SERVER-93213 the setting of metadata within CollectionImpl for 2 timeseries flag has been encapsulated within a helper so that are always set correctly. As a consequence, setting _metadata without that helper may result in catalog inconsistencies.

The current implementation makes the responsibility spread over multiple classes and harder to reason. We should provide a better API to avoid developers to introduce bugs, for example by encapsulating _metadata in an internal class only exposing setters and getters.

The class should also encapsulate the logic on how to set those 2 flags on both the constructor and the parser