[ParidelPooya]

Fixes #806.

Summary

The warning for an unknown outcome of the worker's own SuspendMicrovm call no longer says that jobs are refused once the refusal has already ended. It now states that the refusal ended during the call, that the worker accepts jobs, and when it tries the call again.

Why

1. Without a terminate hook, the warning said: "The worker refuses jobs until the MicroVM resumes, or for 30 seconds."
2. A resume hook during the call ends the refusal. The 30-second limit of a suspend hook's refusal can also end during the call.
3. After an unknown outcome, the worker starts a new refusal only while _suspending is still set.
4. So in these sequences a job right after the warning gets HTTP 202. The fix(microvm-worker): wait at least 30 s after a suspend refused for now #799 review measured this in three sequences: a resume hook, a suspend hook then a resume hook, and a suspend hook whose 30 seconds ended during the call.
5. So the warning stated a refusal that had already ended.

Changes

• _failed_call_warning reads suspending for an unknown outcome. The caller reads it under the lock, as before.
• Refusal ended and the worker is not closed: "the suspend call for the idle MicroVM had an unknown outcome. The refusal of jobs already ended during the call, on a resume hook or after 30 seconds. So the worker accepts jobs. It tries the call again one idle time after the call and every job end."
• Refusal ended after close(): "…So the worker accepts jobs. The worker is closed, so it does not try the call again." A closed worker starts no idle time.
• A job can start during the call after a resume hook. A running job cancels the idle time. So the next call comes one idle time after the call and every job end, not at the outcome. The text says so.
• README item 8 and the listener docstring item 8 now end with: "A resume hook during the call, or the end of a suspend hook's 30 seconds during the call, has already ended the refusal. The worker then accepts jobs at once, and tries the call again one idle time after the call and every job end."
• The terminating text and the normal unknown text are unchanged. Docstring items 8 to 10 of _failed_call_warning describe the cases.
• The decision-block comment now says that the text matches the decision for a rejection and a refusal for now. For an unknown outcome, the second locked block decides whether the 30-second refusal starts. The window between the two blocks existed on main and is tracked in MicroVM worker: the unknown-outcome warning and its refusal are decided in two locked blocks #820. This PR does not change it.
• Behavior is unchanged. The texts and conditions match the JavaScript change in fix(microvm-worker): state that jobs are accepted after an unknown outcome whose refusal ended aws-durable-execution-sdk-js#1069, for MicroVM worker: the unknown-outcome warning says jobs are refused after the refusal ended aws-durable-execution-sdk-js#1056.

Testing

• The three sequences, with and without a job. Each test asserts the full text logged once, and the next call one idle time after the call or the job end. The job cases also assert a 202 for a job right after the warning.
• A job that starts during the call after a resume hook and still runs at the outcome. A second job gets 202. No call starts while a job runs. The next call comes one idle time after the last job ends.
• The case of close() and a resume hook during the call. It logs the closed text, a job gets 202, and no call follows.
• Guards that keep the old text while the refusal lasts: no hook, a suspend hook still in effect, and close() alone. Each gets 503 until 30 s after the call, then 202. Also a resume-then-terminate case that keeps the terminating text.
• Mutation check on the first commit: removing, inverting, or reordering the new branch fails 1 to 17 tests.
• hatch run dev-microvm-worker:cov: 450 passed, worker.py at 100 %. Typecheck, hatch fmt --check, and commit lint pass. Stress run with -n 8, twice: 450 passed.

[yaythomas]