Test/compare show output dco

[mneha05]

Fixes #12675.

Description

This updates the existing ToPrettyString integration coverage so DataFrame.show() output is compared between CPU and GPU execution.

The test now:

• creates the same date/string projection used by the existing ToPrettyString coverage;
• orders the input by str_col before rendering so the textual comparison is deterministic;
• captures df.show() output separately for the CPU and GPU runs;
• uses the repository-prescribed assert_gpu_and_cpu_are_equal_collect helper to verify CPU/GPU execution and result equality;
• compares the captured CPU and GPU display output after the prescribed assertion completes.

The earlier custom SHOW assertion helper has been removed, so the shared assertion infrastructure is unchanged and local-sort handling is unaffected.

Validation:

• isolated capture/comparison regression simulation passed;
• DCO sign-off check passes;
• full Spark/GPU integration workflows are pending maintainer approval on this external-contributor PR.

This change is test-only and does not alter runtime code or performance.

AI assistance was used to explore the repository, implement the test changes, and review the diff. I reviewed the final changes before submission.

Checklists

Documentation

• Updated for new or modified user-facing features or behaviors
• No user-facing change

Testing

• Added or modified tests to cover new code paths
• Covered by existing tests
• Not required

Performance

• Tests ran and results are added in the PR description
• Issue filed with a link in the PR description
• Not required

[greptile-apps]

Confidence Score: 5/5

[Low risk] Test file refactors output capture for a date casting test.

The PR appears safe to merge based on the reviewed changes.

Summary

The PR updates a date-formatting integration test to compare captured CPU and GPU show() output, use a collect assertion, and order its rows deterministically.

_{Reviews (2) · Last reviewed commit: "test: align imports with style"}

[mneha05]

test: compare ToPrettyString show output on CPU and GPU