Add on_demand_scan routes

• Related issue: #227221 (closed)

What does this MR do?

This adds the routes required for the upcoming DAST Site Profiles features which requires an index route where the profiles library will be shown, and a new route for creating DAST Site Profiles.

The routing looks like this:

• index: /:namespace/:project/-/on_demand_scans/profiles
• new: /:namespace/:project/-/on_demand_scans/profiles/site_profiles/new

How to test this?

• Enable the :security_on_demand_scans_feature_flag feature flag.

echo "Feature.enable(:security_on_demand_scans_feature_flag)" | spring rails c

• Navigate to the new pages by appending their path to some project's URL:
  • /:namespace/:project/-/on_demand_scans/profiles
  • /:namespace/:project/-/on_demand_scans/profiles/site_profiles/new

Screenshots

/:namespace/:project/-/on_demand_scans/profiles	/:namespace/:project/-/on_demand_scans/profiles/site_profiles/new

Does this MR meet the acceptance criteria?

Conformity

• [-] Changelog entry (not needed as this is behind the :security_on_demand_scans_feature_flag feature flag)
• [-] Documentation (if required)
• 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