Flatten results from a collection of BitstringAccumulators into a list

of ObservableMeasuredResult.

Raw results are contained in BitstringAccumulator which contains structure related to how the observables were measured (i.e. their grouping). This can be important for taking covariances into account. This function removes that structure, giving a flat list of results which may be easier to work with.

grouped_results A list of BitstringAccumulators, probably returned from measure_observables or measure_grouped_settings.