Fix/use intstr intorstring

[rahul810050]

What this PR does

This PR adds full support for using intstr.IntOrString for spec.driver.cores and spec.executor.cores in SparkApplication. This allows users to specify CPU cores as either:

• Integers (e.g. 1, 2), or
• Fractional CPU values (e.g. "100m", "0.5")

This enhancement enables fine-grained CPU allocation for Spark driver and executor pods on Kubernetes and aligns the API with native Kubernetes resource semantics.

FIxed issue: #2688.

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Why this is needed

Currently, spec.[driver|executor].cores only accepts integers, which prevents users from requesting less than 1 CPU core. In many real-world workloads (especially development, testing, and cost-optimized clusters), fractional CPU requests such as 100m or 0.25 are required.

This PR removes that limitation while preserving backward compatibility.

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Summary of changes

API changes

• Updated SparkPodSpec.cores to use *intstr.IntOrString instead of *int32.
• Regenerated CRDs so that the OpenAPI schema accepts both integer and string values.

Spark submission logic

• Updated internal/controller/sparkapplication/submission.go to:
  • Correctly parse IntOrString values.
  • Convert fractional CPU values to integers using ceiling logic before passing them to:
    • spark.driver.cores
    • spark.executor.cores
• This preserves Spark’s requirement that these configuration values must be integers.

Resource quota validation

• Updated internal/webhook/resourcequota.go to:
  • Convert both integer and string CPU values to milliCPU.
  • Ensure accurate quota validation when fractional CPUs are used.

Defaulting logic

• Updated api/v1beta2/defaults.go to set default cores using intstr.FromInt(1) instead of int32.

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Backward compatibility

• Existing SparkApplications that specify integer values for cores continue to work without any changes.
• No breaking changes to existing users.

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Example usage after this change

driver:
  cores: "100m"

executor:
  cores: "0.25"

Behavior:

• Kubernetes receives a fractional CPU request.
• Spark receives an integer value (rounded up to 1) as required.

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