use HEX values for SD in all APIs

• Use 6-digit HEX in all SBI interfaces
• receiving (e.g. from NRF)
• sending (towards SMF and UDM)

@tien-thinh.nguyen not yet tested E2E but it requires oai-cn5g-smf!248 (merged) and oai-cn5g-upf!37 (merged)

oai-cn5g-common-src!64 (merged)