Add functional tests for cFE Message extended header APIs

[zanzaben]

Is your feature request related to a problem? Please describe.
Need open source functional tests for certifiability

Describe the solution you'd like
Add functional tests for cFE Message extended header APIs
CFE_MSG_GetEDSVersion - Gets the message EDS version.
CFE_MSG_SetEDSVersion - Sets the message EDS version.
CFE_MSG_GetEndian - Gets the message endian.
CFE_MSG_SetEndian - Sets the message endian.
CFE_MSG_GetPlaybackFlag - Gets the message playback flag.
CFE_MSG_SetPlaybackFlag - Sets the message playback flag.
CFE_MSG_GetSubsystem - Gets the message subsystem.
CFE_MSG_SetSubsystem - Sets the message subsystem.
CFE_MSG_GetSystem - Gets the message system.
CFE_MSG_SetSystem - Sets the message system.

Describe alternatives you've considered
N/A

Additional context
These test are being split off from #1677

Requester Info
Alex Campbell GSFC

[skliper]

Note these tests only apply to a build configured to use the extended headers. Recommended approach is to put these in a test app that only gets compiled if configured to use extended headers. Although I guess we could compile either way, it just won't load if the APIs aren't implemented.