fix: Add ClusterCIDRReady condition

[AlexeyPetroff]

Fixes #7875

Summary

This PR addresses an issue where EC2NodeClass resources using AL2023 AMI family would become stuck in a NotReady state after temporary EKS API unavailability. The problem occurs when attempting to resolve Cluster CIDR during reconciliation - if the API call fails, the resource remains in a NotReady state indefinitely, even after the API becomes available again.

Changes

• Added a new condition type ConditionTypeClusterCIDRReady to track the status of Cluster CIDR resolution separately
• Modified the Readiness controller to manage this specific condition instead of directly setting the general Ready condition
• Added the new condition to the list of required conditions in the validation controller

Tested by:

1. Creating an EC2NodeClass with AL2023 AMI family
2. Temporarily revoking EKS DescribeCluster permissions to simulate API unavailability
3. Verifying the EC2NodeClass transitions to NotReady state
4. Restoring permissions
5. Verifying the EC2NodeClass correctly transitions back to Ready state during the next reconciliation

Does this change impact docs?

• [x] Yes, PR includes docs updates
• [ ] Yes, issue opened: #
• [ ] No

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.

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[AlexeyPetroff]

Should be resolved by #8408