Adds Python bindings to Adiak

[ilumsden]

Follow up to Slack discussions with @michaelmckinsey1.

This PR adds Python bindings to Adiak, similar to those added to Caliper.

Like Caliper, these bindings consist of 2 parts:

1. A C++-to-Python bridge implemented with pybind11
2. A small Python library that wraps the bridge code

Also similar to Caliper, these bindings are installed to lib[64]/pythonX.Y/site-packages/pyadiak (where "X.Y" refers to the Python version used during build).

[ilumsden]

Pinging @slabasan and @tpatki since this could be useful for PerfFlow Aspect.

[michaelmckinsey1]

Changes added are tested at this point for single rank, adding integer value from python application. Need to test multi-rank and other types.

Edit: Tested for multi-rank with communicator and different types.

[daboehme]

Thanks, nice work! Would be great to get an example, a test case, and documentation before we merge it in.

[daboehme]

Also, I think it would be good to make MPI an optional dependency for the Python interface as well.

[michaelmckinsey1]

@daboehme Added docs. I was thinking of updating this example https://software.llnl.gov/Caliper/PythonSupport.html#caliper-python-api to add Adiak and then reference that as an example. Thoughts?

[daboehme]

@daboehme Added docs. I was thinking of updating this example https://software.llnl.gov/Caliper/PythonSupport.html#caliper-python-api to add Adiak and then reference that as an example. Thoughts?

I think it would be good to have a chapter in the Adiak docs for the Python API with a small Caliper-free example specifically for Adiak.

We can eventually add a combined Adiak/Caliper example too that can go into the Caliper documentation or tutorial. That's out of the scope for this PR though.

[michaelmckinsey1]

Ok added a test, and documentation (+ example). @daboehme Can we try running the workflow again?