External SST::Statistics libraries do not have access to core simulation object

[jleidel]

Is your feature request related to a problem? Please describe.
SST provides the ability to construct external libraries that provide SST::Statistics mechanisms to store simulation telemetry to orthogonal storage mediums. This is analogous to the console and CSV statistics interfaces. Currently, external statistics libraries cannot access the core simulation object. For example, the following code in the CSV statistics interface cannot be used in externally developed statistics libraries:

https://github.com/sstsimulator/sst-core/blob/master/src/sst/core/statapi/statoutputcsv.cc#L92C14-L92C46

Describe the solution you'd like
We would like to request an API that permits external statistics libraries to retrieve and/or query the core simulation object in order to determine the number of ranks (et al. degree of parallelism). Other bits of info might be interesting as well.

Describe alternatives you've considered
We've attempted to get around this for MPI-centric simulations by retrieving the number of ranks from the MPI_COMM_WORLD communicator object. This is not ideal as we really shouldn't need to access MPI directly from external libraries.

Additional context
No other additional context required.

[gvoskuilen]

This is a useful addition and should be relatively straightforward to support. I'm going to mark "in progress" to denote that we're looking into enabling this.