Refactor code so SonarQube is happy

[CHiPs44]

Code is more and more complex and difficult to update, refactor it until SonarQube for IDE does not choke on:

• Complexity > 25 for some functions
• Const pointers
• ...

I already made:

• CMake handle clang in addition to gcc as they don't compile the same way
• Tests with gcc and clang
• Github action that builds and launch tests for gcc and clang at each commit
• Add NOSONAR comments when reported issue is too cumbersome
• ...