Clean-up syntax for xAOD::Truth-based GeneratorFilters Algorithms (part 1)
Use Gaudi properties, ToolHandles and ReadHandleKeys where possible.
No output changes expected.
(Part 1 of 7, see also !78287 (merged), !79134 (merged), !79135 (merged), !79136 (merged), !79137 (merged), !79138 (merged))
Edited by John Derek Chapman