Add AftersynchronizedProcessing Time as continuation trigger

[tarun-google]

Fixes #34212

In extension to previously discarded work : #14060

1. Added get_continuation_trigger in parity with Java code base and implemented it in all the triggers.
2. Added the internal AfterSynchronizedProcessing time, as a continuation trigger for the AfterProcessingTime trigger which always fire and move the pipeline forward. This is not in parity with Java code with waits for synchronized time
3. Added get_continuation_trigger impl for all the non time based triggers in parity with java code.

GitHub Actions Tests Status (on master branch)

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[tarun-google]

Tested YAML Iceberg pipeline working as expected after introducing this trigger . Failed tests look irrelevant.

Test: https://pantheon.corp.google.com/dataflow/jobs/us-central1/2025-08-20_07_48_19-15906637132818554356;bottomTab=WORKER_LOGS;expandBottomPanel=true;graphView=0;logsSeverity=INFO?pageState=(%22dfTime%22:(%22s%22:%222025-08-20T14:48:20.254Z%22,%22e%22:%222025-08-20T14:50:27.459Z%22))&project=apache-beam-testing

[tarun-google]

R: @ahmedabu98 @kennknowles

[github-actions]

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[derrickaw]

Hi @tarun-google - please fix the lint issues. Looks like some imports are incorrectly sorted. Thanks!

[ahmedabu98]

Generally LGTM, but I think @kennknowles should do a pass too

[kennknowles]

Looks good. I did a quick pass to check against Java just to make sure they are consistent. (not worrying too much about if they are ideal, just as long as they match it is the right thing to do )

[derrickaw]

Run Python_Transforms PreCommit 3.12

[kennknowles]

Please get the tests green (either by re-running or fixing real issues) and I'll merge.

[kennknowles]

If there are new very-flaky tests, please file bugs for them. There may already be bugs filed based on other workflows being flaky, but figuring out which tests are the flakes would be very useful.

[derrickaw]

Run Python_Examples PreCommit 3.10

[derrickaw]

Run Python_Integration PreCommit 3.9

[tarun-google]

Thanks @kennknowles & @derrickaw for triggering 👍 I will follow up the tests

[tarun-google]

Run Yaml_Xlang_Direct PreCommit

[tarun-google]

Run Python_Runners PreCommit 3.9

[tarun-google]

All green Yay 🥇

[liferoad]

Runner V2 does not support this yet. Revert this.