chore(kuttl): add test for failing spark job

[sweb]

Description

Adds two kuttl integration test suites: failure-propagation, which verifies that a Spark application failing at runtime is reported with phase Failed and its driver Pod cleaned up, and graceful-shutdown, which verifies that SIGTERM reaches the executor and driver JVMs so that shutdown hooks run and the driver asks its executors to stop.

Tests for stackabletech/docker-images#1595

Definition of Done Checklist

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Author

• Changes are OpenShift compatible
• CRD changes approved
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• Code contains useful comments
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• (Integration-)Test cases added
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Acceptance

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[razvan]

A nit from Claude which I like is that the test should be more appropriately called signal-propagation, but I'll leave it up to you to change it or not.

[sweb]

A nit from Claude which I like is that the test should be more appropriately called signal-propagation, but I'll leave it up to you to change it or not.

addressed in cf6402c

[razvan]

lgtm. fails as expected with the dev image. didn't try the actual fix in docker-images.

clarification:

1. graceful-shutdown passes with dev
2. signal-propagation fails with dev