cleanup(gke): remove redundant switch in GenerateGKENodeSelectorLabel

[kadupoornima]

Simplify GenerateGKENodeSelectorLabel by Removing Redundant Switch.

The Problem

The GenerateGKENodeSelectorLabel function maps accelerator types to GKE node selector labels. It contains a hardcoded fallback switch statement for "direct values":

// Fallback for direct values
switch resolvedLower {
case "nvidia-tesla-a100", "tpu-v4-podslice", "tpu-v6e-slice", "tpu-v5p-slice", "tpu-v5-lite-podslice":
    return acceleratorType
}

This switch statement is completely redundant. If any of these values (or their prefixes) are passed to the function, they do not match any keys in the machineFamilyToLabelMap. As a result, the function naturally falls through all checks and returns acceleratorType unmodified at the end of the function anyway.

Maintaining this hardcoded list of direct values in a switch statement in addition to the map increases maintenance overhead and leads to duplication.

The Solution

Remove the redundant switch block entirely. Let the function rely on its natural fall-through behavior, which already returns the input string if no map keys match.

The Impact

• Code Simplicity: Reduces the size and complexity of the function, making it easier to read and maintain.
• Maintainability: Eliminates the risk of developers forgetting to keep the switch statement in sync with the map when adding new accelerators.

[gemini-code-assist]

Summary of Changes

Hello, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request cleans up the GKE job orchestrator by removing an unnecessary switch block that handled direct accelerator values. Since the function already defaults to returning the input string when no map matches are found, the switch was redundant. The change simplifies the codebase and improves maintainability, supported by newly added unit tests to verify the expected behavior.

Highlights

• Code Simplification: Removed a redundant switch statement in GenerateGKENodeSelectorLabel that was unnecessary due to the function's existing fall-through logic.
• Test Coverage: Added a comprehensive suite of unit tests for GenerateGKENodeSelectorLabel to ensure correct behavior for mapped families, unmapped values, and case sensitivity.

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[gemini-code-assist]

Code Review

This pull request removes a redundant fallback switch block from the GenerateGKENodeSelectorLabel function in gke_job_orchestrator.go and introduces a comprehensive unit test suite TestGenerateGKENodeSelectorLabel in gke_job_orchestrator_test.go to verify the label generation logic under various scenarios (including mapped families, old switch fallbacks, unmapped values, and case insensitivity). There are no review comments, and I have no additional feedback to provide.

[Neelabh94]

nit: Can you please remove this stray TODO as well.
LGTM otherwise