Refactored CortexM.reset() into several methods.
Refactored CortexM.reset() into several methods.

- Extracted some logic into _get_actual_reset_type() and
  _perform_reset() methods.

pyocd/pyOCD,mbedmicro/pyOCD,mbedmicro/pyOCD,mbedmicro/pyOCD,mesheven/pyOCD,flit/pyOCD,pyocd/pyOCD,mesheven/pyOCD,flit/pyOCD,mesheven/pyOCD