Visually align system bots (Alert, Support, and Security)

Problem

Context: based on recent discovery: #197349 (closed), this introduces a GitLab-Security-Bot, similar to the Alert and Support bot - which are system created bots. The profile of the Security-Bot aims to be abundantly clear that it's a system bot; reinforced by the text, bot emoji, and documentation. The support bot profile can be seen here: https://gitlab.com/support-bot.

Problem: the visual display of the existing bots are not aligned or consistent. Users may get confused about where the bot came from and/or not recognize it's a system-generated user.

Solution

Update alert and support bot avatars with new avatars

• https://gitlab.com/support-bot (doc page)
• https://gitlab.com/alert-bot (related issue: 404 error: #211616 (closed), may need to confirm this is the correct url)
  • Confirmed that this is a bug, fix is !35711 (merged), and we also need to run a migration (!35960 (merged)) to fix the records for existing bot users.
• Security bot avatar to be added later #216027 (closed) will link related issue

Visuals

Figma original	ZIP file
Bot avatars in Figma	Bot-Avatars.ZIP

earlier proposal details

Align system bots with: * Profile includes a link to the documentation stating bot's task, where it may be seen, and what to expect. * Visual avatars that align, perhaps not the same, but communicate it's a GitLab system bot * Distinction the reinforces they are system bots (such as emoji in status: 🤖)

Security bot could use: security tanuki (svg version) for interim needs