Fix compilation problem and compiler warnings

MCStepLogger had compilation issues with conflicting C++ versions
appearing on the command line. This is avoided by a CMakeList simplification.

Also fixing few compilation warnings related to inconsistent virtual + override.

Fix for C++20

std::vector has a constexpr destructor in C++20, which makes forward
declaration not viable anymore.

Migration of MCReplayEngine to vmc v2.0 (#30)

* Migration of MCReplayEngine to vmc v2.0

* Fixed typo in workflow step name

Fallback to ROOT without VMC standalone

Build against VMC standalone (required)

Update READMEs

Updated copyright headers in all files with new text

* Updated copyright headers in all files with new text agreed in the O2 project