Use `CFE_MSG_PTR` instead of `&(x).Msg`

Checklist (Please check before submitting)

[x] I reviewed the Contributing Guide.
[x] I reviewed the CF README.md file to see if the feature is in the major future work.
[x] I performed a cursory search to see if the feature request is relevant, not redundant, nor in conflict with other tickets.

Is your feature request related to a problem? Please describe. &(x).Msg has been abstracted by CFE_MSG_PTR to avoid internal dependencies on CFE_MSG_Message_t

src/cf_app.c:    CFE_MSG_SetMsgTime(&CF_AppData.hk.tlm_header.Msg, CFE_TIME_GetTime());
src/cf_app.c:    /* return value ignored */ CFE_SB_TransmitMsg(&CF_AppData.hk.tlm_header.Msg, true);
src/cf_app.c:    CFE_MSG_Init(&CF_AppData.hk.tlm_header.Msg, CFE_SB_ValueToMsgId(CF_HK_TLM_MID), sizeof(CF_AppData.hk));
src/cf_app.c:    CFE_MSG_Init(&CF_AppData.cfg.tlm_header.Msg, CFE_SB_ValueToMsgId(CF_CONFIG_TLM_MID), sizeof(CF_AppData.cfg));
src/cf_cmd.c:    CFE_MSG_SetMsgTime(&CF_AppData.cfg.tlm_header.Msg, CFE_TIME_GetTime());
src/cf_cmd.c:    /* return value ignored */ CFE_SB_TransmitMsg(&CF_AppData.cfg.tlm_header.Msg, true);

Describe the solution you'd like Use CFE_MSG_PTR

Describe alternatives you've considered None

Additional context None

Requester Info Jacob Hageman - NASA/GSFC

nasa / CF

Use `CFE_MSG_PTR` instead of `&(x).Msg` #199