GHA: run tests on draft PRs

[jsiirola]

Fixes # .

Summary/Motivation:

We moved to more actively using "Draft" PRs to communicate PR status between PR authors and the Review team. Unfortunately, we previously had GHA skip all tests when the PR was marked either "draft" or "WIP", which beans developers aren't getting build/test information. This PR updates the GHA runners so that tests are run for draft PRs, but not for tests marked "WIP".

As a bonus, this reworks the logic around code coverage: the runners are more standardized now, which also means that branches will get coverage computed on their jobs - but not uploaded to codecov.

Changes proposed in this PR:

• Only skip GHA tests for "[WIP]" PRs (and run tests for draft PRs)
• Standardize logic for running coverage

Legal Acknowledgement

By contributing to this software project, I have read the contribution guide and agree to the following terms and conditions for my contribution:

1. I agree my contributions are submitted under the BSD license.
2. I represent I am authorized to make the contributions and grant the license. If my employer has rights to intellectual property that includes these contributions, I represent that I have received permission to make contributions and grant the required license on behalf of that employer.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 89.98%. Comparing base (c1ce36d) to head (5a95227).

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3926      +/-   ##
==========================================
- Coverage   89.98%   89.98%   -0.01%     
==========================================
  Files         904      904              
  Lines      106891   106891              
==========================================
- Hits        96191    96189       -2     
- Misses      10700    10702       +2     

Flag	Coverage Δ
builders	29.15% <ø> (+<0.01%)	⬆️
default	86.31% <ø> (?)
expensive	35.59% <ø> (?)
linux	87.45% <ø> (-2.03%)	⬇️
linux_other	87.45% <ø> (+<0.01%)	⬆️
oldsolvers	28.09% <ø> (+<0.01%)	⬆️
osx	82.82% <ø> (ø)
win	85.88% <ø> (-0.01%)	⬇️
win_other	85.88% <ø> (-0.01%)	⬇️

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[michaelbynum]

Nice! I just have one question. Assuming the answer is no, this looks good to me.

[michaelbynum]

I don't really know what this is doing. Will this prevent people from running tests on branches on forks?

[michaelbynum]

Oh, this is just codecov. Never mind.

[jsiirola]

Exactly: we were getting weird behavior on codecov when branches from forks (including the main branch on forks), and when the "branches" workflow would upload coverage results. THis logic makes sure that only the Pyomo main branch, as well as any PR builds are uploaded to codecov.