Query whether a 'mirai', 'mirai' value or list of 'mirai' remains unresolved.
Unlike call_mirai(), this function does not wait for completion.
unresolved(x)Logical TRUE if x is an unresolved 'mirai' or 'mirai' value or the
list contains at least one unresolved 'mirai', or FALSE otherwise.
Suitable for use in control flow statements such as while or if.