Add unit tests for attachablePodForObject function

[GautamBytes]

Added unit test for pkg/internal/polymorphichelpers/attachablepodforobject.go .

Our tests successfully validated all the logic paths that don't require a live Kubernetes connection:

• The case where the object is already a pod.
• The error path if the REST config fails.
• The error path if SelectorsForObject fails (e.g., for an unsupported type).

The uncovered code is the final "success path" where the function tries to:

• Create a real Kubernetes clientset.
• Use that clientset to find and retrieve a running pod.

This part of the code is not covered because a simple unit test cannot create a real Kubernetes client and connect to the API.

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[GautamBytes]

@furykerry @FillZpp just pinging for review. Thanks!

[GautamBytes]

@furykerry @FillZpp just pinging for review. Thanks!

@furykerry PTAL!

[GautamBytes]

@furykerry @hantmac will you merge these test pr's please!