retryWith
Awaits the outcome of this MessageHandle, retrying according to policy if the send fails with a retryable failure.
Non-retryable failures (SendFailure.Disconnected, SendFailure.Cancelled, SendFailure.HandshakeFailed) abort immediately regardless of remaining attempts.
Requires that MessageHandle.packet and MessageHandle.resendFn are non-null (i.e., the handle was produced by RadioClient.send or RadioClient.sendText, which always populate these fields).
Return
the final SendOutcome (success after any attempt, or the last failure)
Parameters
policy
the retry strategy to apply