The functions of the RAN API should not return the types of OAI, but protobuf
types. Previously, they would return OAI types and the calling code "marshals"
this into Protobuf type. This commit changes the following functions and
modifies the calling code to directly store the protobuf type:
* flexran_get_hopping_mode()
* flexran_get_phich_resource()
* flexran_get_phich_duration()
* flexran_get_ul_cyclic_prefix_length()
* flexran_get_dl_cyclic_prefix_length()
* flexran_get_duplex_mode() usage
* flexran_get_enable64QAM()

* Hello msg agent->RTC carries ID and capabilities this agent supports
* RAN API provides ID and capabilities:
    - flexran_get_bs_id()
    - flexran_get_capabilities() // protobuf list of capabilities
    - flexran_get_capabilities() // capabilities as bit mask

Add FlexRAN capabilities mask RAN API function

Merge branch 'feature-127-protocol-split' of https://gitlab.eurecom.fr/oai/openairinterface5g into feature-127-protocol-split

preparation for UE CONTEXT Release from CU