fix(ci): generate kube config

[universal-itengineer]

Description

Improved test/dvp-static-cluster/scripts/gen-kubeconfig.sh kubeconfig generation flow and error handling.

• Refactored retry logic to avoid redundant checks of the same kubeconfig and made retries explicit at generation level.
• Added robust failure handling and clearer exit behavior:
  • strict bash mode (set -Eeuo pipefail)
  • centralized error-exit helper (exit_with_error)
  • signal/error traps with meaningful exit codes and diagnostics

Why do we need it, and what problem does it solve?

Sometimes the token for kubeconfig is generated incorrectly.

users:
- name: nested-sa
  user:
    token: ��e. #<--

What is the expected result?

Kubeconfig generation retries are performed in one place with predictable attempt count and delay.

Checklist

• The code is covered by unit tests.
• e2e tests passed.
• Documentation updated according to the changes.
• Changes were tested in the Kubernetes cluster manually.

Changelog entries

section: ci
type: chore
summary: fix generate kube config