Create auto-fix user callout

• Related issue: #247543 (closed)

What does this MR do?

This creates the user callout for letting users know about the auto-fix feature.

The callout:

• Appears above the Project Security Dashboard.
• Contains a link to the documentation about auto-fix.
• Is dismissible.
• Doesn't appear again once dismissed (cookie-based preference).
• Will be removed altogether after being shows for a ~2 releases timelapse.

How to test this?

1. Enable the :security_auto_fix feature flag.

echo "Feature.enable(:security_auto_fix)" | rails c

2. Browse to a project's Security Dashboard.

Screenshots

auto_fix_uc

Does this MR meet the acceptance criteria?

Conformity

• [-] Changelog entry (behind a feature flag)
• [-] Documentation (if required) #247882 (closed)
• Code review guidelines
• [-] Merge request performance guidelines
• Style guides
• [-] Database guides
• Separation of EE specific content

Availability and Testing

• Review and add/update tests for this feature/bug. Consider all test levels. See the Test Planning Process.
• [-] Tested in all supported browsers
• [-] Informed Infrastructure department of a default or new setting change, if applicable per definition of done