Deprecate usage of MARS in O3DE Jenkins

[brianherrera]

This PR deprecates the usage of MARS, a metrics collection service that is no longer being supported.

The following components are removed:

• Jobs: collects AR job data and pushes to external endpoint
• Node Configs
• Credentials: Service user that allows external resources (e.g. AWS lambda) to trigger MARS jobs.
• Env vars

[amzn-changml]

Is there still logic in the Jenkinsfile pipeline that also calls out to MARS?

[brianherrera]

Is there still logic in the Jenkinsfile pipeline that also calls out to MARS?

Yes there is. I'll submit a PR to the o3de repo to remove it. At least the steps are non-blocking and it also won't run if MARS_REPO isn't defined anymore.