Remove C++ code support

.flake8

.pre-commit-config.yaml

bob/__init__.py

bob/extension/__init__.py

bob/extension/boost.py

bob/extension/cmake.py

bob/extension/config.py

bob/extension/data/config_with_module.py

bob/extension/data/load_config.py

bob/extension/data/resource_config.py

bob/extension/data/subpackage/config.py

bob/extension/download.py

bob/extension/include/bob.extension/defines.h

bob/extension/include/bob.extension/documentation.h

bob/extension/log.py

bob/extension/pkgconfig.py

bob/extension/rc_config.py

bob/extension/scripts/__init__.py

bob/extension/scripts/click_helper.py

bob/extension/scripts/config.py