Externals Update, main branch (2023.08.23.)

Updated all projects to atlasexternals-2.0.167.

This is a replacement for !65126 (closed), which had to be stopped because of unforeseen changes coming from a GeoModel update. But in the meanwhile I collected a few other updates as well. So the full list of changes wrt. atlasexternals-2.0.165 became (atlasexternals@2.0.165...2.0.167):

• Updated COOL and CORAL to version 3.3.14 (part of the C++20 migration, thanks to @elmsheus);
• Updated Coin3D to hash 5297f6c (part of the C++20 migration, thanks to @rbianchi);
• Made the Gaudi build itself set up Vc for the build/runtime environment (part of the LCG_104 migration, thanks to @elmsheus);
• Made multiple fixes to how AtlasCompilerSettings.cmake sets up the -march=x86-64-v2 build flag;
  • Made it explicitly check whether the used compiler understands -march=x86-64-v2 before it would set it up (Making it possible to still use GCC <11 with our code, for instance for building AnalysisBase).
  • Also made it check whether some other architecture setting is already active before adding the default -march=x86-64-v2;
• Updated lwtnn to version 2.14 (thanks to @voigt);
• Introduced FindCppcheck.cmake into AtlasLCG (thanks to @fwinkl);
• Added explicit support for Rocky Linux in AtlasCMake and AtlasLCG (thanks to @elmsheus).

All these updates still warrant a full suite of tests, even in the absence of a GeoModel update...