Support controlling SparkApplication labels mutation to spark pods

[everpeace]

Purpose of this PR

Proposed changes:

• Introduce SparkApplication.Spec.{Driver,Executor}.SparkApplicationLabelMutation field which provides users to control which labels in SparkApplication are mutated to the Spark pods

kind: SparkApplication
metadata:
  name: spark-app
  labels:
    keyA: valueA
    keyB: valueB
spec:
  driver:
    sparkApplicationLabelsMutation:
      labelKeysMatches:
      - fixed: keyA
  executor:
    sparkApplicationLabelsMutation:
      labelKeysMatches:
      - regex: '^.*'
----
#
# Above SparkApplication generates Spark driver/executor pod like this:
#
kind: Pod
metadata:
  labels:
    # SparkApplication's label
    # keyB is excluded because "keyB" doesn't match "fixed: keyA"
    keyA: valueA

    # managed labels should not be controlled by users
    spark-role: driver
    sparkoperator.k8s.io/launched-by-spark-operator: "true"
    sparkoperator.k8s.io/app-name: spark-app

---
kind: Pod
metadata:
  labels:
    # SparkApplication's label
    # all the labels are mutated because any label key matches "regex: '^.*'"
    keyA: valueA
    keyB: valueB

    # managed labels should not be controlled by users
    spark-role: executor
    sparkoperator.k8s.io/launched-by-spark-operator: "true"
    sparkoperator.k8s.io/app-name: spark-app

Change Category

• Bugfix (non-breaking change which fixes an issue)
• Feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that could affect existing functionality)
• Documentation update

Rationale

Fixes #2669

Checklist

• I have conducted a self-review of my own code.
• I have updated documentation accordingly.
• I have added tests that prove my changes are effective or that my feature works.
• Existing unit tests pass locally with my changes.

Additional Notes

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[ChenYi015]

It is a bit compliated for users to use a field like sparkApplicationLabelsMutation when integrating with Kueue. Let us use the controller-reference way first and see wether the community has a request for this feature.
/hold for review

[everpeace]

ref: #2669 (comment)

As discussed in the community meeting on 2025-10-17, we plan to introduce a simpler solution.