Update coverage workflow, report separate unit vs integration

[rly]

Motivation

Our code coverage workflow runs only unit tests, however, the coverage percentage considers all lines of code in pynwb, including the IO module code, which is not run by the unit tests.

This PR changes the coverage workflow to run the unit tests and integration tests separately, adds flags "unit" and "integration" to each codecov upload so that we can distinguish them and get separate coverage percentages, and also updates the rest of the workflow to newer versions of Actions.

Checklist

• Did you update CHANGELOG.md with your changes?
• Have you checked our Contributing document?
• Have you ensured the PR clearly describes the problem and the solution?
• Is your contribution compliant with our coding style? This can be checked running flake8 from the source directory.
• Have you checked to ensure that there aren't other open Pull Requests for the same change?
• Have you included the relevant issue number using "Fix #XXX" notation where XXX is the issue number? By including "Fix #XXX" you allow GitHub to close issue #XXX when the PR is merged.

[codecov]

Codecov Report

Merging #1509 (f165e69) into dev (2dc6351) will increase coverage by 11.88%.
The diff coverage is n/a.

@@             Coverage Diff             @@
##              dev    #1509       +/-   ##
===========================================
+ Coverage   78.64%   90.52%   +11.88%     
===========================================
  Files          37       25       -12     
  Lines        2777     2460      -317     
  Branches      517      456       -61     
===========================================
+ Hits         2184     2227       +43     
+ Misses        510      148      -362     
- Partials       83       85        +2     

Flag	Coverage Δ
integration	69.87% <ø> (?)
unit	83.94% <ø> (?)

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
src/pynwb/legacy/io/icephys.py
src/pynwb/legacy/io/epoch.py
src/pynwb/legacy/io/ophys.py
src/pynwb/legacy/map.py
src/pynwb/legacy/io/file.py
src/pynwb/legacy/io/misc.py
src/pynwb/legacy/io/behavior.py
src/pynwb/legacy/io/image.py
src/pynwb/legacy/io/ogen.py
src/pynwb/legacy/io/base.py
... and 15 more

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[oruebel]

Looks good to me. Just to clarify, do I understand the changes correctly that with this we should get 3 coverage reports: 1) unit only, 2) integration tests only, 3) combined coverage?

[rly]

Yes. I am not sure you can view each report separately on the codecov website though.

I remembered we have badges in the README. I just updated the badges to report those 3 report percentages.