Update GitHub Workflows

[mjtrangoni]

Hi,

This PR intend to get the CI Workflows to a current state-of-the-art status.

• Update the base runner images from Ubuntu 20.04 to 22.04.
• Replace EOL centos:7 with rockylinux:8
• Remove EOL ubuntu:16.04, adds ubuntu:24.04
• Update checkout workflow
• Configure dependabot

[mjtrangoni]

@uli42 PTAL. We should fix/adapt some of the linters results like python3 issues (Shall we remove python2 support?).
Also cppcheck and GCC are updated as well, and may report some newer issues/fixes.

PVS licenses should be ok again the next time we merge something.