[roll] Roll fuchsia [fidl][cpp] Remove WireSyncEventHandler::Unknown

Now that HandleOneEvent returns a fidl::Status, there is no concern of
status clashing, and we can reliably indicate an unknown event error
(represented with an error with `fidl::Reason::UnexpectedMessage` as the
reason).

This makes it easier to add unknown interactions handling, since there
won't be two subtle concepts of unknown events (one flexible, one
strict) occurring at the same time.

Since the usage of sync event handling is not that widespread, we could
migrate all of them atomically. I did a best-effort migration to
preserve the existing behavior, but there are some delta:

- in fdio::create_with_on_open, we now transform all errors to ZX_ERR_IO
  except peer-closed.
- some tests may have a small delta in failure log messages.

Original-Reviewed-on: https://fuchsia-review.googlesource.com/c/fuchsia/+/668305
Original-Revision: c889b5bb0981307972c8c13a696c7c88fdea64f2
GitOrigin-RevId: b8f1c4b570a2c6b255e1d41c6e9a85c613e7ea91
Change-Id: If0e7655d304348e1b920d7b95b7b6c2fb197620a