x-lang GroupByEncryptedKey (Java to Python)

[damccorm]

This PR adds some x-lang tests to test that the gbek option works when calling across languages from Java to Python. Most of the fixes in this PR are related to that (+131 lines). As part of this work, though, I also noticed/fixed 2 problems:

1. Pipeline options weren't being respected across this boundary; to fix this, I added a way to merge pipeline options in pipeline_options.py, and then used that instead of the previous very incomplete merging logic in expansion_service.py. Before, we hadn't been doing anything with these options anyways when calling in from Java because of Fix passing pipeline options to external transforms #36443.
2. Incorrect coders were being used coming out of GBEK because it wasn't recognizing the output types. I fixed this by explicitly calling with_output_types at the end of the expansion_service.py.

#36457 contains the Python -> Java version of these tests.

Part of #36214

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 36.21%. Comparing base (c8df4da) to head (5258999).

Additional details and impacted files

@@              Coverage Diff              @@
##             master   #36418       +/-   ##
=============================================
- Coverage     55.02%   36.21%   -18.82%     
  Complexity     1666     1666               
=============================================
  Files          1058     1058               
  Lines        165254   165291       +37     
  Branches       1190     1190               
=============================================
- Hits          90939    59865    -31074     
- Misses        72138   103249    +31111     
  Partials       2177     2177               

Flag	Coverage Δ
python	40.54% <ø> (-40.41%)	⬇️

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[damccorm]

Moved Python -> Java tests to #36457 for clarity since this now has functional changes, not just test changes.

[damccorm]

Now seeing xvr failures with:

java.lang.RuntimeException: org.apache.beam.sdk.coders.CoderException: `UnknownCoderWrapper` was used to perform an actual decoding in the Java SDK. Potentially a Java transform is being followed by a cross-language transform that uses a coder that is not available in the Java SDK. Please make sure that Python transforms at the multi-language boundary use Beam portable coders.
	at org.apache.beam.sdk.util.construction.UnknownCoderWrapper.decode(UnknownCoderWrapper.java:55)
	at org.apache.beam.sdk.coders.Coder.decode(Coder.java:159)
	at org.apache.beam.sdk.coders.LengthPrefixCoder.decode(LengthPrefixCoder.java:64)
	at org.apache.beam.sdk.coders.KvCoder.decode(KvCoder.java:83)
	at org.apache.beam.sdk.coders.KvCoder.decode(KvCoder.java:37)
	at org.apache.beam.sdk.values.WindowedValues$FullWindowedValueCoder.decode(WindowedValues.java:847)
	at org.apache.beam.sdk.values.WindowedValues$FullWindowedValueCoder.decode(WindowedValues.java:838)
	at org.apache.beam.sdk.values.WindowedValues$FullWindowedValueCoder.decode(WindowedValues.java:784)
	at org.apache.beam.sdk.fn.data.BeamFnDataInboundObserver.multiplexElements(BeamFnDataInboundObserver.java:232)
	at org.apache.beam.fn.harness.control.ProcessBundleHandler.processBundle(ProcessBundleHandler.java:527)
	at org.apache.beam.fn.harness.control.BeamFnControlClient.delegateOnInstructionRequestType(BeamFnControlClient.java:150)
	at org.apache.beam.fn.harness.control.BeamFnControlClient$InboundObserver.lambda$onNext$0(BeamFnControlClient.java:115)
	at java.base/java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:515)
	at java.base/java.util.concurrent.FutureTask.run(FutureTask.java:264)
	at org.apache.beam.sdk.util.UnboundedScheduledExecutorService$ScheduledFutureTask.run(UnboundedScheduledExecutorService.java:163)
	at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1128)
	at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:628)
	at java.base/java.lang.Thread.run(Thread.java:829)

I'd seen this locally, but had thought I'd moved past it (and did get at least one green run here). Will debug further, it seems like it could be an issue with type inference

[damccorm]

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[damccorm]

/gemini review

[gemini-code-assist]

Code Review

This pull request adds cross-language tests for GroupByEncryptedKey (GBEK) from Java to Python, and includes several important fixes for cross-language pipeline option handling and coder inference. The changes in the Python SDK for merging pipeline options and explicitly setting output types are well-implemented. The new Java test for GBEK is a great addition. I've suggested a few improvements to the test code to handle resources more safely and to make the failure test case more robust.

[chamikaramj]

LGTM. Thanks!