milder termination condition for optMLx example

[mmckerns]

Summary

use a milder, more consistent, termination for the optML"x" loop by looking at the error at the minimum. Print other potential error metrics that are informative. Other minor cleanup of optML examples.

Checklist

Documentation and Tests

• Artifacts produced with the main branch work as expected under this PR.

Release Management

• Added rationale for any breakage of backwards compatibility.