[sx1278] Refactored Fsk driver to be more like LoRa driver

src/shared/radio/SX1278/SX1278Common.h

src/shared/radio/SX1278/SX1278Defs.h

src/shared/radio/SX1278/SX1278Frontends.h

src/shared/radio/SX1278/SX1278Fsk.cpp

src/shared/radio/SX1278/SX1278Fsk.h

src/shared/radio/SX1278/SX1278Lora.cpp

src/shared/radio/SX1278/SX1278Lora.h

src/tests/radio/sx1278/fsk/common.h

src/tests/radio/sx1278/fsk/test-sx1278-bench-gui.cpp

src/tests/radio/sx1278/fsk/test-sx1278-bench-serial.cpp