Persist value stream stages

What does this MR do?

• Utilises the new endpoint in !51623 (merged) allowing us to submit value stream stages to the create endpoint (previously only accepted the name of the value stream)
• Submits value streams with their related stages for persisting
• Handles rendering server errors along the corresponding form field

Screenshots (strongly suggested)

Value stream from no template
480-vsa-no-template

Feature flag

There are 2 feature flags required to see these changes:

• value_stream_analytics_path_navigation: enables the path navigation UI
• value_stream_analytics_extended_form: enables the additional form fields added here in the create value stream form

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 #297370 (closed)