[Testing] Add lifecycle regression tests for grpcserver and optimistic sync pipeline

[janezpodhostnik]

Adds regression coverage for the two component-lifecycle fixes from #8633. Each new test was verified to fail with the corresponding fix reverted, and to pass with it.

Changes

• module/grpcserver: first tests for the package. Verify a normal start/stop lifecycle throws nothing, that an immediate shutdown racing startup does not throw ErrServerStopped (50 iterations amplify the race between the shutdown worker's GracefulStop and the serve worker reaching Serve), and that a genuine listen failure is still thrown as irrecoverable.
• optimistic sync pipeline: verify a parent state update delivered before Run is not lost when Run is invoked with a stale initial parent state. Before the fix, the pipeline deadlocked in StateWaitingPersist and never persisted; the test drives it to StateComplete.

Related: #8633

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