CI: improve unit test workflow in CI, revert #2046

[fangchenli]

Reference Issues or PRs

xref: #1128

What does this implement/fix?

Put a x in the boxes that apply

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds a feature)
• Breaking change (fix or feature that would cause existing features not to work as expected)
• Documentation Update
• Code style update (formatting, renaming)
• Refactoring (no functional changes, no API changes)
• Build related changes
• Other (please describe):

Testing

• Did you test the pull request locally?
• Did you add new tests?

Any other comments?

The original goal of this PR is to reduce the installation time. But then I discovered that we were not really testing multiple Python versions. When the CI is configured correctly, the Python 3.12 build from #2046 will not work due to the lack of wheels for conda-build and multiple other dependencies for Python 3.12.

In this PR, I reverted #2046, fixed the unit test build so it actually ran on different Python versions, added auto cancelation, and reduced the installation time from ~20min to ~ 1min.

[iameskild]

Good catch @fangchenli!

vs now: