patch: Use get-workflow-version action instead of workflow

[carlcsaposs-canonical]

Use GitHub API (via composite action) to get workflow versions instead of recursively checking out repositories

https://github.com/canonical/get-workflow-version-action

Benefits:

• less runners used (1 less job)
• faster
• (side effect, not specific to API vs checkout) uses SHA hash to avoid race conditions if ref updated after workflow triggered but before it run
• works on private repositories (if GitHub token passed with correct permissions)

[carlcsaposs-canonical]

build_charm.yaml tested on https://github.com/canonical/data-platform-arm-runner-test/actions/runs/8941412675/job/24561678731