[#51679461] Refactor 'hasCommitMessage' in Activity model to ignore the action type.
[#51679461] Make WorkFlowUpgradedVersion events appear in activity streams

- Add WorkFlowUpgradedVersion event to fixture builder (ruby).
- Add workFlowUpgradedVersion to fixture definitions (js).
- Add event definition to ActivityPresenter (js).
- Add translation for the activity header
[#51679461] refactor ActivityPresenter to make private field names more clear

- Extracted the headerDefinitions out of 'hidden'.
- Renamed 'hidden' to 'presenterHelpers'.
[#51679461] clarify the purpose of the modifier_id on the WorkfileVersionsController#create endpoint