[.backport v2.13.6] Previously set add on values are not preserved on cluster view and edit

[rancher-ui-project-bot]

This is a .backport issue for #17498, automatically created via GitHub Actions workflow initiated by @eva-vashkevich

Original issue body:

Setup

• Rancher version: 2.13.5-master
• Rancher UI Extensions: None
• Browser type & version: Any

Describe the bug

Add-on chart values are not preserved on cluster view and edit.

To Reproduce

1. Create an RKE2 cluster with cilium selected as an add on and any k8s version v1.33.x. Set non-default cilium chart's values ie

ingressController:
          default: false
          enabled: true
          loadbalancerMode: shared

2. Save
3. Go to view the cluster. Cilium config is displayed correctly when viewed as yaml, but not when viewed as config.
4. Go to edit the cluster. Upgrade k8s version (or edit any other unrelated field). Save

Result
Cilium configuration is reset to default.

Expected Result

1. Add-on charts' values should be preserved when viewing the cluster.
2. Add-on charts' values should be preserved if cluster was edited.

Screenshots

Additional context

These steps to reproduce are just one example of broken functionality. Any add on could be affected and should be validated.
Editing clusters as YAML is not affected