Optionalsignal: AbortSignalTrue only when the external caller signal initiated cancellation.
Composite signal aborted by either the caller or the absolute deadline.
True when the absolute startup deadline has elapsed.
Release the deadline timer and external abort listener.
Milliseconds still available to the next startup phase.
Wait for at most one polling interval under the shared deadline signal.
One absolute deadline shared by every phase of a provider startup handshake.
The deadline owns its timer and the listener attached to an optional caller signal. Adapters must dispose it after startup succeeds or fails.