Add 'build_workflow_name' input, to allow overriding where scripts look for artifacts

[jayavenkatesh19]

Uniquely identifying an artifact from the GitHub Actions artifact store requires identifying the workflow run that produced it.

In PR CI, this is trivial because the uploading-artifacts and downloading-artifacts jobs are all running as part of the same workflow.

In other setups though, that isn't true. For example, RAPIDS uses 2 separate nightly workloads:

• build.yaml = build packages and publish the package artifacts
• test.yaml = pull those artifacts and run tests with them

For this case, in the relevant gha-tools scripts we default to assuming that branch or nightly runs want to pull artifacts from runs of a workflow literally called build.yaml:

run_id=$(
  RAPIDS_RETRY_SLEEP=30 \
    rapids-retry --quiet gh run list \
      ... \
      --workflow "${RAPIDS_BUILD_WORKFLOW_NAME:-build.yaml}" \
      ...
)

ref: https://github.com/rapidsai/gha-tools/blob/570fc211e6bf1bfb91098aa1bc4823ef7bb71fc2/tools/rapids-github-run-id#L66

There might be cases in the future where that assumption doesn't hold, and people want to pull artifacts in one workflow run from some other workflow which is NOT called build.yaml.

This PR + rapidsai/shared-actions#52 add support for specifying the name of that "some other workflow" as an input, overriding the build.yaml default.

For more context, see rapidsai/gha-tools#162 (comment)

How I tested this

Tested with an rmm PR: rapidsai/rmm#1909

• does not break existing repos CI: WIP: [DO NOT MERGE] test changes to GitHub Actions configs and scripts rmm#1909 (comment)
• correctly threads this input through to the RAPIDS_BUILD_WORKFLOW_NAME variable: WIP: [DO NOT MERGE] test changes to GitHub Actions configs and scripts rmm#1909 (comment)

[jameslamb]

I've added context for why we're doing this in the description, and re-targeted this at branch-25.08. I need to run right now, but when I return to this I'll get it updated and merge it.

[jameslamb]

I just pushed some changes in c34104a

• custom-job.yaml should be included as well.. it's sometimes used to run tests
• clarified the description for the new build_workflow_name input

I've also changed the PR title to more accurately reflect the goal here.