Externals Update, main branch (2025.03.25.)

Updated all projects to atlasexternals-2.1.47. The changes wrt. atlasexternals-2.1.45 are as follows (atlasexternals@2.1.45...2.1.47):

• Various updates for CheckerGccPlugins (thanks to @ssnyder);
• Introduced (a patched version of) boost-mpi3 0.81 (thanks to @bstanisl);
• Introduced triton-client 24.12 (thanks to @xju);
• Re-wrote the FindHighFive.cmake module to not rely on the CMake code of HighFive.
  • Together with !78758 (merged) and !78776 (merged) it is meant to make our code compatible with LCG_107a_ATLAS_3. See SPI-2757, SPI-2753 and ATLINFR-5716 for details.

None of the existing externals are modified. So let's skip full-integration-tests. But conservatively, let's still do full-build and full-unit-tests. 🤔