FAPI P7 Refactoring and unitary test creation
This MR is a follow-up to the work done in !2714 (merged), this time separating the P7 FAPI messages into its own library (nr_fapi_p7).
In the same way, utility functions to copy, free and compare have been added for each message, as well as an addition function to get the allocated size for a message, which is used for the messages that can be too big to fit in a buffer that's allocated in the stack.
Unitary tests have been added for each of the messages, testing pack/unpack and the utility functions added.