AIP-10276 : Backward compatibility to generate Argo URL based on Argo WF Controller version

[v-abhijeets]

Summary

Adds backward-compatible Argo workflow URL generation for both legacy and modern Argo UI route shapes (AIP-10276, related to AIP-10272).

get_argo_url() now supports two URL formats via ARGO_UI_ROUTE_MODE:

• legacy → {host}/argo-ui/workflows/{ns}/{run_id}?uid={uid}
• modern → {host}/workflows/{ns}/{run_id}

ARGO_UI_ROUTE_MODE=auto (default) probes the Argo UI HTML on ARGO_RUN_URL_PREFIX:

• /argo-ui/ → legacy
• / (or other non-argo-ui href) → modern
• probe failure → safe fallback to legacy

Explicit legacy / modern still override auto-detection.

• Create-time resolved mode + ARGO_RUN_URL_PREFIX are baked into step metaflow_configs and exit-handler env so runtime pods do not need to re-probe the Argo UI.
• Callers (aip_cli.py, exit handlers) stay unchanged — they already use get_argo_url().

Testing

• Added same changes in feature branch of zillow-metaflow gitlab repository and tested URL generation in Integration tests review job
• Tested with newer Argo version 3.7.15 and integration tests are passed with correct Argo URL.
• Tested with older Argo version 3.4.16 and integration test has generated proper Argo URL.

Why this change is needed?

The Argo server was migrated so that the workflow UI is now served directly at
https://<argo-server-host>/workflows/... — the legacy /argo-ui/ path segment
no longer exists. The CI variables in .gitlab-ci.yml were already updated to
point ARGO_RUN_URL_PREFIX at the bare host (e.g.
https://argo-server.int.sandbox-k8s.zg-aip.net/), so get_argo_url() was
producing broken links of the form