[CpuMeter] Separated cpu statistics getter and reset functions

libs/mavlink-skyward-lib

src/shared/diagnostic/CpuMeter/CpuMeter.cpp

src/shared/diagnostic/CpuMeter/CpuMeter.h

src/tests/logger/test-logger.cpp

src/tests/sensors/calibration/test-calibration-benchmark.cpp

src/tests/sensors/test-l3gd20-fifo.cpp

src/tests/sensors/test-l3gd20.cpp