Re-structure order of jet collection recording and modification

Currently the jet reconstruction algorithms create a jet container, modify it, and then record it to the event store. This causes a problem if the modifiers use ReadHandles/DecorHandles on the jets, since they're not yet in the store (see, e.g. !25234 (merged)). This MR restructures things a bit such that the recording happens before any modification, and the WriteHandle for the collection is kept in-scope throughout so that the container isn't locked before this is all done.

Tagging @delsart and @khoo for their awareness (turns out this was a simpler fix than we initially feared).