Closes #3970: comm_diagnostics function to return a DataFrame

[ajpotts]

This PR adds a get_comm_diagnostics() function that returns a DataFrame of diagnostic statistics. It also modifies print_comm_diagnostics to print to the python interpreter in addition to the chapel logs.

Closes #3970: comm_diagnostics function to return a DataFrame

[drculhane]

I pulled and ran this this morning, and it certainly appears to work. Next time we have a team meeting, can you explain why the test does a print? That puzzles me, but I don't see it as a reason not to approve.

[1RyanK]

@drculhane If I understand correctly, lines 61 and 62 of tests/comm_diagnostics_test.py are

print_comm_diagnostics_table(print_empty_columns=True)
print_comm_diagnostics_table(print_empty_columns=False)

These were not edited, so they are easy to miss.
Anyways, because of the edits to that function (specifically lines 114 - 117 of the update):

    if print_empty_columns:
        print(df.to_markdown())
    else:
        print(df[[col for col in df.columns if ak_sum(df[col]) != 0]].to_markdown())

The tests will cause prints.

[jaketrookman]

Looks good