Refactor time tracking

What does this MR do?

Refactor time tracking to use eventHub so that it can be shared with multiple assignees

Are there points in the code the reviewer needs to double check?

Not sure if I setup issuable_bundle.js correctly.

Why was this MR needed?

Prep for real time, less rework for the future.

Screenshots (if relevant)


Does this MR meet the acceptance criteria?


What are the relevant issue numbers?