Add process for generating the combined metrics template and output the optimal value of k

After we have generated the metaprogram metrics and scores for each metaprogram, we need to calculate the final metrics and get our rankings to identify the optimal value of k. This should follow the same template as https://github.com/AlexsLemonade/ews-nf/blob/main/templates/combined-metaprogram-metrics.Rmd.

I think we might want to pull out some of the calculations into one step (including actually identifying the optimal k) and then have the report generation be a separate step, but I will look into this more when I actually implement it.