[FLINK-40568][tests] Fix flaky ProcessTableFunctionSemanticTests by using materialized data assertion

[spuru9]

What is the purpose of the change

Fixes the flaky ProcessTableFunctionSemanticTests for the process-updating-multi-input program, which intermittently fails in CI with an output mismatch:

Expecting actual:
  ["+I[Bob, score 2 in city London]", "+U[Bob, score 2 in city Berlin]"]
to contain exactly in any order:
  ["+I[Bob, score 5 in city London]", "+I[Alice, score 2 in city Zurich]",
   "+U[Bob, score 3 in city London]", "+U[Bob, score 3 in city Berlin]",
   "-D[Bob, null]", "+I[Bob, score 2 in city Berlin]", "-D[Alice, null]"]

The program runs the two-input updating PTF join UpdatingJoinFunction and asserts the sink's raw changelog. A two-input operator interleaves its two inputs nondeterministically, so the emitted changelog is not fixed — the test pinned one interleaving, and an alternate order fails the assertion. The final materialized (upsert) result is the same either way.

Brief change log

• Assert the materialized result for process-updating-multi-input via SinkTestStep#testMaterializedData() instead of the raw changelog, mirroring FLINK-39729 (PR [FLINK-39729][table] Fix flaky CorrelateRestoreTest by using materialized data assertion #28224) and the multi-input join programs (MultiJoinTestPrograms).

Test-only change; no production code is touched.

Verifying this change

The job is awaited to completion, then the sink result is checked. The materialized upsert result is order-independent (Bob → score 2 in city Berlin, Alice deleted), so it no longer depends on cross-input arrival order.

• ProcessTableFunctionSemanticTests (72 cases) passed a repeated local loop on the same commit that failed in CI (JDK 17), with the process-updating-multi-input case green every time.

Does this pull request potentially affect one of the following parts:

• Dependencies (does it add or upgrade a dependency): no
• The public API, i.e., is any changed class annotated with @Public(Evolving): no
• The serializers: no
• The runtime per-record code paths (performance sensitive): no
• Anything that affects deployment or recovery: JobManager (and its components), Checkpointing, Kubernetes/Yarn, ZooKeeper: no
• The S3 file system connector: no

Documentation

• Does this pull request introduce a new feature? no
• If yes, how is the feature documented? not applicable

AI usage disclosure

• Claude Code

[flinkbot]

CI report:

• 8d67b06 Azure: SUCCESS

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[spuru9]

Recent https://github.com/apache/flink/actions/runs/34264705035/job/102194014611

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Another https://github.com/apache/flink/actions/runs/34613631530/job/103313520639