Refactor MR Security Widget

• Refactor MR Security Widget
• Use refactor_security_extension flag

Related to #338283 (closed) &7881 (closed)

Purpose

• Refactor the widget using the new extension API
• To allow for the Security widget extension to be controlled by it's own feature flag, independent from the global refactor_mr_widgets_extensions flag that enables all widgets.

Screenshots

Testing locally

Enable the feature flag:

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

1. Go to any MR
2. (Optional but handy) Download Mokku for mocking the API: https://chrome.google.com/webstore/detail/mokku-mock-api-calls-seam/llflfcikklhgamfmnjkgpdadpmdplmji?hl=en
3. (Optional but handy) Import the following mocks to Mokku mr-security-widget.json
4. Verify that the widget loads. You can play around with the responses to simulate different cases.

Notes

• This MR is based off of the approach taken to allow for License Compliance to to maintain the legacy widget even if we roll out the new license extension !84128 (merged)