Create DAST Configuration page [RUN ALL RSPEC] [RUN AS-IF-FOSS]

What does this MR do?

This MR

• Adds a enable button for DAST in Security Configuration Page.
• Adds a boilerplate page for upcoming DAST Configuration / Settings Page.
• Adds a new feature flag (dast_configuration_ui) and control the aforementioned changes using the flag

Screenshots (strongly suggested)

Before	After (when feature flag is enabled)

How to test this

1. Enable the feature flag.

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

2. Navigate to a project's Security Configuration page at /:namespace/:project/-/security/configuration.
   • You should see the Enable link in the DAST section.
   • Clicking on the link should take you to the empty DAST Settings page

Does this MR meet the acceptance criteria?

Conformity

• I have included a changelog entry, or it's not needed. (Does this MR need a changelog?)
• I have added/updated documentation, or it's not needed. (Is documentation required?)
• I have properly separated EE content from FOSS, or this MR is FOSS only. (Where should EE code go?)
• I have self-reviewed this MR per code review guidelines.
• I have followed the style guides.

Availability and Testing

• I have added/updated tests following the Testing Guide, or it's not needed. (Consider all test levels. See the Test Planning Process.)
• I have tested this MR in all supported browsers, or it's not needed.