Externals Update, main branch (2024.06.13.)

Upgraded all projects to atlasexternals-2.1.18. The (relevant) changes wrt. atlasexternals-2.1.17 are (atlasexternals@2.1.17...2.1.18):

• Introduced Findcoverage.cmake and FindGeneva.cmake into AtlasLCG (thanks to @averbyts and @fwinkl);
• Made AtlasCMake and AtlasLCG detect AlmaLinux a little more robustly (Fixing ATLINFR-5385, thanks to @elmsheus);
• Made the code compatible with CMake 3.29+. (For ATLINFR-5342.)

The updates generally don't need a full-build or full-unit-tests. 🤔 So let's see how the CI does...