Add caching mechanism for QNX builds

[ryan-steel]

What

Our QNX workflows keep failing on a timeout error, see https://github.com/eclipse-score/time/actions/runs/31154121790/job/92789817872?pr=154

We should update to use the latest ci-cd workflows which enable repo cache maintenance to download QNX artifacts to the cache only when MODULE.bazel.lock is changed.

Acceptance Criteria (DoD)

• Caching mechanism implemented in github workflows
• QNX builds don't fail frequently with timeouts

How

Update to use the latest ci-cd workflows, add cache-maintenance workflow.