Summarises a df_vpcstats() result: the run configuration and the column
groups present in stats. Printing it shows the same content as
print.vpc_stats() without the head preview, which suits vignette output
and test snapshots.
Value
A summary.vpc_stats object (also summary.pmx_stats): a list
with header (the class tag, dim of stats, obs_rows, and the
config values n_replicates, ci, pi, mode, loq, strat_var)
and column_groups (a named list of the stats columns in each group:
identifiers, counts, sim_blq, std_observed, std_simulated,
pc_observed, pc_simulated, metadata; empty groups are
character(0)).
