SUSYTools C++20 Fix, main branch (2023.08.21.)
Made SUSYTools build in AthAnalysis against LCG_104 with C++20. Had to include the full definition of all interfaces used in ToolHandleArray<T>
objects, as forward declarations are no longer enough for them.
This is a sibling of !65166 (merged), and is meant to fix ATLASG-2578.