Add link to profile to commit avatar

## What does this MR do?

- links to user profiles to the avatars on commits page
- tooltips to the avatars on commits page

side effect:

- links to user profiles to the avatars on pipelines page
- tooltips to the avatars on pipelines page
- tooltips to the avatars on activity page
- mailto links to the avatars on activity page for non-registered users

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

Nope.

## Why was this MR needed?

There were no links nor Zeldas.

## What are the relevant issue numbers?

fixes #19644 


See merge request !5163