Investigate users’ understanding of iconography

Related to: #26945 (closed)

When conducting usability testing, some users were confused by the iconography GitLab uses. It would be interesting to test some of the icons we use.

[Clip 1] (https://youtu.be/RQGV7y-6uoQ?t=54s), [Clip 2] (https://youtu.be/UF_zfCYgukw?t=1m27s), [Clip 3] (https://youtu.be/UF_zfCYgukw?t=4m10s), [Clip 4] (https://youtu.be/UF_zfCYgukw?t=11m).