TopEvent Cleanup, master branch (2020.11.06.)

Triggered by !37941 (closed) and ATLASG-1569, this is a semi-deep cleanup of the TopEvent package. (It could do with a bit more, but I'll leave that to the Top developers.)

First and foremost the MR updates the "xAOD types" defined by TopEvent to behave properly.

• The individual classes were put into separate header and source files, as is the ATLAS coding standard.
• The dictionary for the classes was moved from a "CINT style" dictionary to a "Reflex style" one. Which we need to use with all xAOD types.
• The code instantiated by ADD_NS_DV_PROXY(...) was moved to the newly created TopEventDict dictionary library from the TopEvent linkable library.
• I removed the xAOD::PseudoTopResultAuxContainer type completely. It defined no static auxiliary variable, so one should just use xAOD::AuxContainerBase in its stead.

Of course all these changes necessitated changes in a bunch of downstream packages as well. Beside having to update some includes, and accounting for the removal of the xAOD::PseudoTopResultAuxContainer type, I also had to clean up the CMake configuration of 2 of the packages. As the cleanup in TopEvent revealed errors in the CMake configuration of those. (And as long as I was updating those files, I re-wrote them completely...)

With all this in place the top-xaod executable at least starts...

Pinging @tdado.