tests: stabilize timeout waits

[Carter Tinney (cartertinney)]

What changed

• distinguish prompt polling, scheduled cross-thread/event-loop completion, and longer eventual waits
• scale batch completion bounds by the number of queued handler effects
• apply the timeout semantics consistently across sync and async handler-manager tests

Why

Handler callbacks are dispatched through runner threads, event loops, and thread-pool workers. Treating those effects as immediately completable with a 100 ms bound caused timing-sensitive failures under full-suite coverage load even though the expected exception handling completed.

The tests continue polling the actual observable effects; production behavior is unchanged.

Validation

• affected sync tests: 50/50 repeated runs
• related handler-manager and loop tests: 230 passed
• Python 3.11 full suite with coverage: 5,454 passed
• Ruff and Black checks passed

[Copilot]

🟢 Approval recommended

The focused test-only changes consistently apply the documented timeout semantics without unresolved issues.

Pull request overview

Stabilizes timing-sensitive asynchronous tests without changing production behavior.

Changes:

• Adds timeout constants for scheduled and eventual completion.
• Scales batch waits by queued handler effects.
• Applies consistent timeout semantics across synchronous and asynchronous tests.

File summaries

File	Description
tests/unit/helpers.py	Defines distinct timeout categories.
tests/unit/iothub/test_sync_handler_manager.py	Stabilizes synchronous handler waits.
tests/unit/iothub/aio/test_async_handler_manager.py	Stabilizes asynchronous and batch handler waits.
tests/unit/iothub/aio/test_loop_management.py	Extends concurrent loop-creation waits.

Review details

• Files reviewed: 4/4 changed files
• Comments generated: 0
• Review effort level: Balanced

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