Replace onebox.go [wip]

[stephanos]

What changed?

This PR is the parent branch for removing the duplicated onebox setup and moving the remaining test customization points onto narrower testcore/testhook APIs.

Related split PR: #10336

Why?

We want to eliminate WithFxOptionsForService so testcore no longer needs an unrestricted Fx escape hatch when it moves away from duplicating the production service setup.

TODO: remove WithFxOptionsForService blockers

Split PRs and remaining call-site groups:

• Replace direct DCRedirectionPolicy decoration in tests/xdc/failover_test.go with typed WithDCRedirectionPolicy: Add test cluster DC redirection policy option #10328
• Replace one tests/dlq_test.go DLQ observation decoration with await-based polling: Remove one WithFxOptionsForService from tests/dlq_test.go  #10338
• Replace xdc/ndc history and namespace replication task executor decorations with focused test hooks: Remove WithFxOptionsForService from xdc/history_replication_signals_and_updates_test.go #10322
• Replace remaining tests/dlq_test.go history task execution decoration with fault injection/test hooks: Remove one more WithFxOptionsForService from tests/dlq_test.go #10336
• Replace TestAddTasks_GetEngineErr functional coverage with a focused unit test: Migrate TestAddTasks_GetEngineErr to unit test #10337
• Migrate tests/purge_dlq_tasks_api_test.go and replace its persistence decoration with runtime fault injection: Migrate tests/purge_dlq_tasks_api_test.go #10339
• Replace tests/schedule_migration_test.go frontend ContextMetadataInterceptor decoration with a focused typed TestEnv option backed by startup dynamic config: Replace schedule migration Fx option with dynamic config #10400.
• Replace tests/xdc/history_replication_dlq_test.go history replication executor / DLQ writer / namespace replication executor decorations with focused test hooks or testcore options: Remove xdc history replication DLQ Fx decorations #10389
• Replace remaining xdc DCRedirectionPolicy decorations in stream_based_replication_test.go and delete_execution_replication_test.go with WithDCRedirectionPolicy: Use typed DC redirection policy option in xdc tests #10349
• Remove TestWithFxOptionsForService, since it only verifies the generic escape hatch.
• Remove testcore.WithFxOptions / WithFxOptionsForService API once all call sites are gone.

How did you test it?

Validation is tracked in the split PRs above.

Rebase validation on latest main:

go test -tags test_dep ./common/testing/testhooks ./temporal ./tests/testcore ./tests -run "TestAddTasks_GetEngineErr|TestDLQSuite|TestPurgeDLQTasksSuite|TestFunctionalTestBase|TestWithFxOptionsForService" -count=1

Potential risks

The main risk is missing one of the existing WithFxOptionsForService call sites while splitting the work across smaller PRs.

[stephanos]

There are many more refactorings that can be done here, but keeping it to an absolute minimum here.