scripts: runners: generalize --no-load argument

Move the existing "--no-load" argument from the OpenOCD and Intel Cyclone V
runners into an argument in the runners base class such that it can be used
by all runners. Also update the existing runners to work with the common
option instead of their own.

Signed-off-by: Mathieu Choplain <mathieu.choplain-ext@st.com>