[Enhancement] Validation workflow YUM need to pull pgp key based on repo file

[peterzhuamazon]

[Enhancement] Validation workflow YUM need to pull pgp key based on repo file

2025-03-18 22:07:59 INFO     Valid URL - https://artifacts.opensearch.org/releases/bundle/opensearch/3.x/opensearch-3.x.repo and Download Successful !

2025-03-18 22:07:59 INFO     Valid URL - https://artifacts.opensearch.org/releases/bundle/opensearch-dashboards/3.x/opensearch-dashboards-3.x.repo and Download Successful !

2025-03-18 22:07:59 INFO     Executing "sudo rpm --import https://artifacts.opensearch.org/publickeys/opensearch.pgp" in /tmp/tmph23vl9q6

Instead of hardcoding location of https://artifacts.opensearch.org/publickeys/opensearch.pgp, we need to pull the key url from .repo file instead as 3.0 GA will use a different key.

Thanks.