[Develop] Add an end2end test to validate the proxy use case

[hehe7318]

Description of changes

• Added a new integration test to validate the proxy use case.
• Use cloudformation/proxy/proxy.yaml to deploy the proxy environment.
  • The proxy environment includes necessary networking, instances, and security groups.
• The test performs the following steps:
  1. Deploy the proxy environment using the CloudFormation stack.
  2. Create a ParallelCluster using the proxy environment.
  3. Connect to HeadNode through bastion.
  4. Check internet access by trying to access google.com
  5. Submit a sleep job to the cluster and verify its successful completion.

Tests

• Locally test can pass successfully now.

References

• Proxy CloudFormation template (see https://github.com/aws/aws-parallelcluster/blob/develop/cloudformation/proxy/proxy.yaml)

Checklist

• Make sure you are pointing to the right branch.
• If you're creating a patch for a branch other than develop add the branch name as prefix in the PR title (e.g. [release-3.6]).
• Check all commits' messages are clear, describing what and why vs how.
• Make sure to have added unit tests or integration tests to cover the new/modified code.
• Check if documentation is impacted by this change.

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