chore: Remove examples that are related to EKS Blueprints cluster modules

[bryantbiggs]

What does this PR do?

• Remove the following examples:
  • ingress-controllers/nginx - doesn't provide additional value beyond enabling the addon, addon is shown in other examples already
  • node-groups/* - no longer required due to use of terraform-aws-eks module
  • portworx - doesn't provide additional value beyond enabling the addon, currently does not work due to the IAM policy (should use IRSA but currently does not support)
  • upstream-with-k8s-addons - no longer required since nearly all examples will be following this approach (soon)
  • gitlab-ci-cd - this example didn't show anything relevant to EKS and instead just demonstrated using GitLab for Terraform remote state management. A proper example is slated to be implemented in [BLUEPRINT]Replace gitlab-ci-cd with an example that shows self-hosted GitLab on EKS #493

Motivation

• Relates to Update documentation for v5 changes #868
• Updating examples to start showing what the future plan is for examples/blueprints without introducing any breaking changes to users
• Relates to chore: Refactor examples to leverage terraform-aws-eks for cluster creation #1074

More

• Yes, I have tested the PR using my local account setup (Provide any test evidence report under Additional Notes)
• Yes, I have added a new example under examples to support my PR
• Yes, I have created another PR for add-ons under add-ons repo (if applicable)
• Yes, I have updated the docs for this feature
• Yes, I ran pre-commit run -a with this PR

Note: Not all the PRs require a new example and/or doc page. In general:

• Use an existing example when possible to demonstrate a new addons usage
• A new docs page under docs/add-ons/* is required for new a new addon

For Moderators

• E2E Test successfully complete before merge?

Additional Notes

[Zvikan]

LGTM