MEDIUM: cli: apply spelling fixes for known commands before listing them

MEDIUM: cli: apply spelling fixes for known commands before listing them

Entering "show tls" would still emit 35 entries. By measuring the distance
between all unknown words and the candidates, we can sort them and pick the
10 most likely candidates. This works reasonably well, as now "show tls"
only proposes "show tls-keys", "show threads", "show pools" and "show tasks".

If the distance is still too high or if a word is missing, the whole
prefix list continues to be dumped, thus "show" alone will still report
the entire list of commands beginning with "show".

It's still impossible to skip a word, for example "show conn" will not
propose "show servers conn" because the distance is calculated for each
word individually. Some changes to the distance calculation to support
updating an existing map could easily address this. But this is already
a great improvement.