Use hex values in RabbitMQ Streams protocol description

The protocol documentation uses decimal values for error and request key
codes.

Let's use hex values instead. This helps when looking at a request and
its response - 0x0006 and 0x8006 vs. 6 and 32774.

Also, when looking at output of protocol analysis tools like Wireshark,
a hexadecimal value will be printed, for example:

    "Nov  1, 2021 23:05:19.395825508 GMT","60216,5552","00000009000600010000000701"
    "Nov  1, 2021 23:05:19.396069528 GMT","5552,60216","0000000a80060001000000070001"

Above, we can visually identify delete publisher request and response
(0x0006 and 0x8006) and easily match them in the documentation of the
protocol.

Finally, above argument applies to logging as it is common to log
hex values, not decimal.

(cherry picked from commit 08c417f)

Author: wrobell