MEDIUM: cli: increase the payload pattern up to 64 bytes

MEDIUM: cli: increase the payload pattern up to 64 bytes

The maximum size allowed for the payload pattern was increase up to 64 bytes
(65 bytes because of the trailing \0), to be able to use a sha256 of random
data for instance. It could be useful to prevent any data smuggling on the
payload.

Note that on the CLI, it could be possible to have only the buffer size as a
limit, because the command line is only consumed once all commands are
executed. The payload pattern is only a pointer in the buffer where the
command line was copied. However, for the master CLI, the data are streamed
to the worker, so we must keep a copy of he payload pattern. This is why we
must limit its size.