[FEA] Add build/run environment output as a separate step in build/test workflows

[wence-]

Often when CI fails during package upgrades it is because the dependencies are not yet up to date in the installed environment. Spotting this is sometimes complicated because either the test run script doesn't run the relevant command (conda list or pip freeze), or it's lost in installation/test run backtraces.

It would be nice if there were a step in the actions workflow that just ran conda list or pip freeze as a appropriate that we could expand as a step in the CI run.

I think it would have to run after the repository-provided test script (or else the workflows would have to split the "create environment" from the "run tests" phase).

We could do this ad-hoc in each repository's run script, but that doesn't give nice clicky sections in the CI run, and is easy to miss because it's not always in a consistent place.

[davidwendt]

Also, conda env builds now seem to fill the logs with alot of empty lines. Example: https://github.com/rapidsai/cudf/actions/runs/13006776830/job/36275298458#step:10:57

Perhaps we could suppress this output in favor of just a consistent, easy to locate pip freeze or conda list output section.

[vyasr]

See rapidsai/ci-imgs#228 for more discussion of the conda log lines issue.