Bring part of Time Tracking to CE

See this comment and my response: https://about.gitlab.com/2016/12/08/announcing-gitlab-enterprise-edition-premium/#comment-3045813029

Time tracking, since its release, has been hugely popular. The demand to make it available for everyone has been very strong. We've seen that teams of all sizes, not only teams > 100 members, were interested in this feature. Therefore, we are bringing the current state of time tracking (slash commands + sidebar information) to CE.

Advanced reporting related to time tracking will remain exclusive to EE Premium.

Proposal

• Move the slash commands and sidebar information to CE

References

• API for time tracking: https://gitlab.com/gitlab-org/gitlab-ce/issues/25861