* use python3 on debians too
in Debian 11 which is Bullseye, /usr/bin/python is a Python2
interpreter, which means that cppcheck-htmlreport fails to run here.
So I've chenged the shebang to use python3
* change all shebangs from python to python3
Co-authored-by: Sam M W <smw@alertergroup.co.uk>