Add multi HTTP support

What does this MR do?

A smallish MVC to bootstrap the beginning of adding multiple HTTP integration endpoints through the new form for Category:Incident Management

Design

This merge supports this Epic: &4442 (closed) and will come in the following stages:

Merge	You are here
Add initial wrapper for new form and feature flag	🤘
Add GraphQL to new form and build out HTTP steps	TBA
Build out Prometheus steps for new form	TBA
Add ee support to add multiple endpoints	TBA
Allow users to delete added endpoints	TBA
Allow users to edit added endpoints	TBA
Remove feature flag(UX review happens here to keep the cost of work low) and delete old form code / REST API code	TBA

Screenshots (strongly suggested)

Current Form	New Form Base(Hidden behind feature flag )

Does this MR meet the acceptance criteria?

Conformity

• [-] Changelog entry
• [-] 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
• [-] Informed Infrastructure department of a default or new setting change, if applicable per definition of done

Security

If this MR contains changes to processing or storing of credentials or tokens, authorization and authentication methods and other items described in the security review guidelines:

• [-] Label as security and @ mention @gitlab-com/gl-security/appsec
• [-] The MR includes necessary changes to maintain consistency between UI, API, email, or other methods
• [-] Security reports checked/validated by a reviewer from the AppSec team

Related to #255603 (closed)