Further improvements to Slack integration test reporting

[andrewmogan]

A couple of suggestions from Kurt at today's SWI&T meeting:

1. Have the summary message distinguish between modules and tests. Right now, everything is listed as a "test."
2. Make the pytest log directory not appear as a clickable link. Based on some cursory Googling, this will require formatting it as a code block, since using single backticks is apparently not sufficient.