Add Vendor comand to ConfirmationUI support msg_formatting

This is not a HAL change. It just adds a command to msg_formatting.h as
a service to vendors who have to augment the protocol between the HAL
service and the TA or other implementation with janitorial commands that
don't effect the HAL interface.

Bug: 76152930
Test: No functional change
Change-Id: I5d4e5dadea29d4c7d51753939eda6c3f3571fae1