account: use string_view, cleanup

src/call.h

src/ip_utils.cpp

src/ip_utils.h

src/jamidht/jamiaccount.cpp

src/jamidht/jamiaccount.h

src/sip/sipaccount.cpp

src/sip/sipaccount.h

src/sip/sipaccountbase.h

src/sip/sipvoiplink.cpp

src/sip/sipvoiplink.h