Map Feature Flag userWithId Strategy Parameters Between BE and FE

What does this MR do?

This MR makes a change to our new version feature flags so that the new frontend and backend match up.

For a userWithId strategy, the backend stores the strategy parameters as a list with no spaces: { userIds: 'user1,user2,user3' }

The legacy frontend maps this to a list with spaces for display purposes: user1, user2, user3

The legacy frontend also maps this back to a list without spaces for the backend: user1,user2,user3

The new frontend for the new version flags was not doing this mapping, and this MR makes it do so.

This MR also introduces new feature specs for the new version feature flags.

Issue: #35555 (closed)

Screenshots

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