E3-670: Propose linters

This MR adds cppcheck to our pre-commit configuration. It also addresses a number of (easier) issues, and highlights at least one remaining open issue. For our own convenience, a few rules have been ignored/filtered out, and the job as a whole is allowed to fail.

This MR also appends a .clang-format configuration file to specify that we follow Google's style guide. This was initially since also cpplint was added, which is a tool made by Google that (as default) expects their style guide to be followed.