REGTESTS: log: check that the +cbor output passes the logged bytes through

REGTESTS: log: check that the +cbor output passes the logged bytes through

The encoding described in section 8.6 deliberately does not apply to the
cbor encoding, whose default output form is already made of hex digits and
whose "+bin" form emits delimited binary blocks. Nothing checked that so
far, so a well-intentioned change could reintroduce an encoding there
without anyone noticing.

Check that a byte outside the printable range, a UTF-8 sequence and a '#'
all reach the CBOR text string untouched, that a binary sample goes to a
byte string with its byte preserved, and that the "+bin" form leaves the
value alone as well.