Externals Update, master branch (2022.10.28.)

Updated all projects to atlasexternals-2.0.142. There is practically just one big change coming with this tag (atlasexternals@2.0.141...2.0.142): The formalism for specifying how to download externals has been unified to use an ATLAS_<EXTERNAL>_SOURCE cache variable in all cases. Which shall allow us to override even the "download mode" of the externals if necessary. (More on that a little further down.)

Updated all build_externals.sh scripts to this new formalism for overriding the version of the externals to be built. After these updates the exact same version of everything should continue to be built. But this new setup should finally fix ATLINFR-4709.

The CI and the regular nightlies will not be affected by this change. However some of the "special" nightlies will be.

• I believe the "LCG nightlies" should continue working fine as they are. But you should keep an eye on them @simmons, just in case.
• The ones which will definitely be affected are the "Gaudi nightlies". @fwinkl, @aundrus, we'll need to update those on the same day on which this MR is merged in.
  • To specify a Git tag/branch for Gaudi to be downloaded for the build, we'll need to use the formalism: -DATLAS_GAUDI_SOURCE="GIT_REPOSITORY;https://gitlab.cern.ch/gaudi/Gaudi.git;GIT_TAG;<branch/tag to use>" Hopefully this will be easy to implement for those nightlies.
• @pagessin, do we have "Acts nightlies" at the moment? If you (or somebody else in Acts) builds such things, those will also need to be updated similar to what I wrote for Gaudi.

I think the rest of the nightlies will not need any modifications. But we'll definitely need to check carefully once this is merged in...