option to override default resources.limits with none

https://argo-workflows.readthedocs.io/en/release-3.5/cost-optimisation/#configure-executor-resource-requests shows how to set default limits (ie cpu/memory) for all workflows

would like ability for one workflow to do an override of setting no limits
i tried `cpu: null` but it did not work

Start with the cost-optimisation documentation section linked in the issue and trace how default executor resource limits are applied to an individual workflow. Confirm the expected behavior for a per-workflow request with no limits, then add or update coverage for that override and verify that existing defaults remain unchanged for other workflows.

Written by the indexing model from the issue text.