Fixes for Gaudi::Functional not using GaudiAlg

This is a backward compatible change needed to prepare for gaudi/Gaudi!1444 (merged).

• explicitly include Gaudi/Accumulators.h
• use GaudiAlgorithm explicitly where needed
• adapt for the change of header file for PyAlg

Part of a set of independent MRs: !3395 (merged) Allen!1193 (merged) Analysis!975 (merged) Boole!466 (merged) LHCb!4082 (merged)

mentioned in merge request LHCb!4082 (merged)

added RTA label

• [2023-04-28 19:18] Validation started with lhcb-master-mr#7737
• [2023-04-28 19:19] Validation started with lhcb-master-mr#7738
• [2023-05-01 19:07] Validation started with lhcb-master-mr#7749
• [2023-05-05 12:58] Validation started with lhcb-master-mr#7789
• [2023-05-05 13:02] Validation started with lhcb-master-mr#7790
• [2023-05-05 13:35] Validation started with lhcb-master-mr#7790
• [2023-05-17 08:46] Validation started with lhcb-master-mr#7886
• [2023-05-22 14:00] Validation started with lhcb-master-mr#7958
• [2023-05-22 14:00] Validation started with lhcb-master-mr#7959

marked this merge request as ready

mentioned in merge request Boole!466 (merged)

changed the description

mentioned in merge request Analysis!975 (merged)

mentioned in merge request Allen!1193 (merged)

approved this merge request

mentioned in issue Moore#574 (closed)

merged

mentioned in commit 6ccb82bc