LCG_97a Update, 1.0 branch (2020.09.09.)

This is to update AnalysisBaseExternals and AthAnalysisExternals to use externals from LCG_97a.

The update brings the following list of changes:

• Boost 1.70.0 --> 1.72.0;
• fjcontrib 1.041 --> 1.044;
• GoogleTest <unknown/untagged> --> 1.10.0;
• HDF5 1.10.3 --> 1.10.5;
• LHAPDF 6.2.3 --> 6.3.0;
• setuptools 41.0.0 --> 44.1.0;
• ROOT 6.18/04 --> 6.20/06;
• TBB 2019_U7 --> 2020_U1;
• XRootD 4.10.0 --> 4.12.2;
• nlohmann_json 3.5.0 --> 3.6.1;

Some of the updates were taken from !722 (merged), either as cherry-picks or by copying the code by hand.

As always, the main motivation is to use a newer version of ROOT in the analysis releases. Which in this case should fix ATLASG-1546.