Tag to be used with the main branch of atlas/athena. Update(s) since 2.1.54: - Small fixes for boost-mpi3 - Update atlasexternals CI to CMake 4.0.1 - CheckerGccPlugins: Fix warning suppression for nested array member - Update atlasexternals CI gcc13 pipelines to gcc14, update CI tests to LCG_107a_ATLAS_11