[sx1278] Moved frontends to separate class, allowing better modularity

cmake/boardcore.cmake

src/entrypoints/sx1278-serial.cpp

src/shared/radio/SX1278/Ebyte.h

src/shared/radio/SX1278/SX1278Common.cpp

src/shared/radio/SX1278/SX1278Common.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/test-sx1278-bench-gui.cpp

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

src/tests/radio/sx1278/fsk/test-sx1278-bidir.cpp

src/tests/radio/sx1278/fsk/test-sx1278-mavlink.cpp

src/tests/radio/sx1278/lora/test-sx1278-bidir.cpp

src/tests/radio/sx1278/lora/test-sx1278-mavlink.cpp

src/tests/radio/sx1278/lora/test-sx1278-simple.cpp