Support `PRESERVE` in Addon `conflictResolution`

[kemv]

/kind feature

Describe the solution you'd like
[A clear and concise description of what you want to happen.]
When defining addons for the EKS cluster, it seems the only conflictResolution methods available are overwrite and none (https://github.com/kubernetes-sigs/cluster-api-provider-aws/blob/main/controlplane/eks/api/v1beta2/types.go#L149).

For my use-case i'd like to use the third method supported by AWS: PRESERVE (see https://awscli.amazonaws.com/v2/documentation/api/latest/reference/eks/update-addon.html). Perhaps it wouldn't be a big change to support this.

Anything else you would like to add:
[Miscellaneous information that will assist in solving the issue.]

Environment:

• Cluster-api-provider-aws version: v2.8.3
• Kubernetes version: (use kubectl version): 1.32
• OS (e.g. from /etc/os-release):

[k8s-ci-robot]

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[damdo]

This was fixed in #5330