Add enhancement for NRI plugin mutation policy

[amritansh1502]

Description:

Problem

OpenShift nodes with NRI can apply merged container adjustments from more than one plugin, so administrators need an explicit rule for which namespaces may receive that combined result and whether enforcement is strict or observe-only. Policy cannot be defined reliably in a single plugin's CreateContainer path because that view does not represent the fully merged adjustment.

Proposal:

This enhancement proposes a standalone NRI policy plugin evaluated at CRI-O's ValidateContainerAdjustment hook, with namespace-scoped rules in v1.

Approach: A Dev Preview (MachineConfig delivery, in scope for this enhancement)

Ship the standalone policy plugin and its policy YAML on worker nodes via MachineConfig/Ignition, and enable NRI through a CRI-O drop-in that loads the plugin. The plugin reads the canonical on-disk policy at /etc/crio/nri_plugins/AllowMutations/config.yaml and enforces it at ValidateContainerAdjustment against the merged adjustment. This approach allows early feedback to be gathered on the policy API shape without committing to a final delivery mechanism.

Approach B: (GA (out of scope, tracked separately):

Based on reviewer feedback, the agreed GA path is to extend the existing ContainerRuntimeConfig (ctrcfg) API with an NRI mutation policy field, delivered via the MCO's existing reconciliation pipeline. The plugin binary is unchanged — only delivery moves from raw Ignition to the ctrcfg API. This will be designed and tracked in a follow-on enhancement once Approach A is proven in Dev Preview.

• Related Jira: [ OCPNODE-3378](https://redhat.atlassian.net/browse/OCPNODE-3378)

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Test name	Commit	Details	Required	Rerun command
ci/prow/markdownlint	e2ef038	link	true	/test markdownlint

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