TauAnalysisTools, etc: Interface to lock decorations produced by TauTruthMatchingTool.

As part of fixing the race condition with decorations and deep copies, we need to ensure that decorations get locked after they're written. TauAnalysisTools was attaching decorations using SG::Decorator and not locking them.

Since the interfaces of TauAnalysisTools take one tau object at a time (and this wasn't straightforward to change), we do this by adding a new interface to lock the decorations after all objects have been processed.

See ATLASRECTS-8008.