Update Buildkite CI pipeline

[quffaro]

Changing pipeline.yml

[github-actions]

Review Checklist

Does this PR follow the development guidelines? Following is a partial checklist:

Tests

• New features and bug fixes have unit tests
• New modules have tests that are ultimately called by the test runner (test/runtests.jl)
• Existing tests have not been deleted
• Code coverage >= 90% or reduction justified in PR

Documentation

• All exported functions, types, and constants have docstrings, written in complete sentences
• Citations are given for any constructions, algorithms, or code drawn from external sources

Other

• Style guidelines are followed, including indent width 2
• Changes breaking backwards compatibility have been approved

[quffaro]

@jpfairbanks the Buildkite CI now passes here with the new dynamic pipeline and build matrix features. The former lets us make organization-wide changes to the build pipeline, while the build matrix lets us test on different combinations of environment variables, which for now is just the Julia version.

This branch allows our CI/CD to use HPC to build/test.

[jpfairbanks]

Tick the task list items off that are true and LGTM

[epatters]

So is the plan to make the benchmarks CI action (which is currently very slow) run in Buildkite? I don't mind merging this PR as long as the CI passes but I don't know what it's actually doing.