make matrix type configurable

[jameslamb]

Closes rapidsai/build-planning#158

Today, the matrix (combinations of job variants) for testing workflows is determined by the "build_type" (one of "branch", "nightly", or "pull-request").

This proposes:

• making the matrix selection configurable
  • so you could for example achieve behavior like "run the nightly test matrix in PR CI"
• adding descriptions on the enum-like inputs, listing the valid values
• expanding input validation
  • to ensure unexpected values result in an immediate, clear, loud error

Notes for Reviewers

How I tested this

See the comments on this PR I used to test: rapidsai/rmm#1865

[jameslamb]

Sad, looks like choice inputs can't be used with the workflow_call trigger

I'd hoped we could use GitHub Actions choice type to implement enum-like behavior (GitHub docs), so that matrix_type and other inputs didn't have to be arbitrary strings.

Looks like that's not possible 😭

The workflow is not valid. In .github/workflows/pr.yaml (Line: 89, Col: 11): Error from called workflow rapidsai/shared-workflows/.github/workflows/conda-cpp-build.yaml@customize-matrix (Line: 6, Col: 15): Unexpected value 'choice' In .github/workflows/pr.yaml (Line: 89, Col: 11): Error from called workflow rapidsai/shared-workflows/.github/workflows/conda-cpp-build.yaml@customize-matrix (Line: 7, Col: 9): Unexpected value 'options'

(run link from RMM test PR)

To be fair, actionlint also reported that but I'd hoped (naively) that it was just wrong or maybe confused because these are shared workflows. Sigh 😭

[ajschmidt8]

I left a comment on .github/workflows/conda-cpp-tests.yaml, but it's relevant to all the test workflow changes.

[vyasr]

Logic looks fine to me.