CFE_EVS_MAX_PORT_MSG_LENGTH size reduction requires clarity

[chillfig]

Is your feature request related to a problem? Please describe.
The 11 bytes needed in CFE_EVS_MAX_PORT_MSG_LENGTH for the downstream downstream EVS_OutputPort() printing is not clearly communicated in #2566.

Describe the solution you'd like
Write a variable to clearly defining the extra storage needed for CFE_EVS_MAX_PORT_MSG_LENGTH. Can be either a runtime variable in EVS_SendViaPorts() or as a #define in modules/evs/fsw/src/cfe_evs_task.h

Describe alternatives you've considered
Leave as-is

Additional context
Rationale for why 11 bytes is currently needed is detailed in #2566
This ticket is written as a result of CCB feedback.

Requester Info
Justin Figueroa, Vantage Systems