[Improvement] Run static fleet checks only if there are static nodes

[himani2411]

Description of changes

• Run static fleet checks if there are any static nodes

ruby_block[wait for static fleet capacity] action run[2025-06-17T15:34:30+00:00] INFO: Processing ruby_block[wait for static fleet capacity] action run (aws-parallelcluster-slurm::finalize_head_node line 197)
[2025-06-17T15:34:30+00:00] INFO: Count of cluster static nodes is 0
[2025-06-17T15:34:30+00:00] INFO: Static fleet capacity is ready

  ruby_block[wait for static fleet capacity] action run[2025-06-17T15:43:04+00:00] INFO: Processing ruby_block[wait for static fleet capacity] action run (aws-parallelcluster-entrypoints::test line 197)
[2025-06-17T15:43:04+00:00] INFO: Count of cluster static nodes is 12
[2025-06-17T15:43:04+00:00] INFO: Static fleet capacity is ready
[2025-06-17T15:43:04+00:00] INFO: ruby_block[wait for static fleet capacity] called

Tests

• Manual test
• ONGOING BELOW

test-suites:
  update:
    test_update.py::test_dynamic_file_systems_update:
      dimensions:
      - instances:
        - c5.xlarge
        oss:
        - alinux2023
        regions:
        - eu-west-2
        schedulers:
        - slurm
    test_update.py::test_dynamic_file_systems_update_data_loss:
      dimensions:
      - instances:
        - c5.xlarge
        oss:
        - rhel9
        regions:
        - eu-west-2
        schedulers:
        - slurm
    test_update.py::test_dynamic_file_systems_update_rollback:
      dimensions:
      - instances:
        - c5.xlarge
        oss:
        - rocky9
        regions:
        - rocky9
        schedulers:
        - slurm
    test_update.py::test_login_nodes_update:
      dimensions:
      - instances:
        - c5.xlarge
        oss:
        - rhel8
        regions:
        - us-east-2
        schedulers:
        - slurm
    test_update.py::test_multi_az_create_and_update:
      dimensions:
      - instances:
        - c5.xlarge
        oss:
        - alinux2
        regions:
        - eu-west-2
        schedulers:
        - slurm
    test_update.py::test_update_slurm:
      dimensions:
      - instances:
        - c5.xlarge
        oss:
        - rhel8
        regions:
        - eu-central-1

References

• Link to impacted open issues.
• Link to related PRs in other packages (i.e. cookbook, node).
• Link to documentation useful to understand the changes.

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

[himani2411]

Opened #2978 as I was not able to update this PR due to GH availability issues