ci: Filter supported versions of EKS

[marseel]

Whenever EKS stopped supporting a particular version of EKS, we had to
manually remove it from all stable branches. Now instead of that, we
will dynamically check if it's supported and only then run the test.

This implementation is not great as supported versions are hard-coded in
eksctl until EKS fixes it: aws/containers-roadmap#982 (comment)
Because of that, we always fetch newest eksctl version.

Followup on #32302

[marseel]

/test

[marseel]

/ci-awscni
/ci-eks

[marseel]

/test

[marseel]

Example run where I added 1.22: https://github.com/cilium/cilium/actions/runs/8923095382/job/24507488689

Removing version 1.22 as it's not supported
Version 1.26 is supported
Version 1.27 is supported
Version 1.28 is supported
Version 1.[29](https://github.com/cilium/cilium/actions/runs/8923095382/job/24507488689#step:7:30) is supported
Filtered matrix:
{
  "include": [
    {
      "version": "1.26",
      "region": "us-west-1"
    },
    {
      "version": "1.27",
      "region": "us-east-2",
      "ipsec": true
    },
    {
      "version": "1.28",
      "region": "ca-central-1",
      "ipsec": true
    },
    {
      "version": "1.29",
      "region": "us-east-1",
      "ipsec": true,
      "default": true
    }
  ]
}

[marseel]

/test