In issues and merge request lists, show merged and closed dates on hover

Problem

In the closed issues list, hovering CLOSED does not show the date the issue was closed. It does, however, show a timestamp for the last time it was updated. This may not always be the date on which the issue was closed.

Proposal

In the issues and merge request lists, when hovering CLOSED, show a tooltip with both the relative and the absolute timestamp of when the issue or merge request was closed.

The same thing should happen for MERGED merge requests.

Original description

### Summary

Hovering over CLOSED in the issue list view does not show the date. The view contains a last updated timestamp, but not when the issue was actually closed.

Steps to reproduce

Navigate to project/issues, click on Closed tab. Hovering over CLOSED does not show the date the issue was closed. It does, however, show a timestamp for the last time it was updated. This may not always be the date on which the issue was closed.

Links

Customer ticket -> https://gitlab.zendesk.com/agent/tickets/93323 (internal)

Edited by Pedro Moreira da Silva