Improve both the clarity and verbosity of pytest outputs

[jiridanek]

We'd like to see what tests were run, with what results, also the log messages, but not be overwhelmed by all that.

Ideas

• the github expanding logs feature

• summary of executed tests at the end of pytest output

• some pytest plugins like sugar and so on

          I wonder whether we should log/print the skipped/ignored files here with the explanation?
  

Originally posted by @jstourac in #871 (comment)

[andyatmiami]

While I did not dig very deeply into it - Codecov apparently has some facilities for including information on tests...

Not sure that meets the criteria here we are looking for - but figured I'd mention it nonetheless

• https://docs.codecov.com/docs/test-analytics

[jiridanek]

Interesting. The Allure reports have similar facilities as well, https://allurereport.org/. I used that in the RStudio PDF rendering test. What's missing there is to make the report accessible, currently GitHub Actions does not preserve it anywhere.

The Coverity thing handles a different thing, summarizing the JUnit xml files. PyTest can produce these out of the box, so we can set it up. Alternative to Coverity here would be some tool that produces the GitHub Summary (the Markdown that can be rendered as part of the GH Actions result page).