getprogname: rename to px4_get_taskname

src/modules/systemlib/err.c

src/platforms/nuttx/px4_layer/px4_nuttx_tasks.c

src/platforms/posix/px4_layer/px4_posix_tasks.cpp

src/platforms/px4_tasks.h

src/platforms/qurt/px4_layer/px4_qurt_tasks.cpp