more use of {fmt}

src/im/message_engine.cpp

src/jamidht/jamiaccount.cpp

src/media/video/video_device.h

src/media/video/video_device_monitor.cpp

src/sip/sdp.cpp

src/sip/sipaccountbase.cpp

src/sip/sippresence.cpp

src/string_utils.cpp

test/unitTest/string_utils/testString_utils.cpp