Skip confirmation user api

What does this MR do?

This merge request adds a parameter for the API to allow admins to create users without email confirmation or update user emails without asking them for an email reconfirmation.

Why was this MR needed?

GitLab current's API implementation allows to create a user specifying the email but it asks for email confirmation, just like the update did (in this case, a reconfirmation on the new email address). With this little change it made sense to have the possibility for admins to avoid the email confirmation while dealing with users via API.

Does this MR meet the acceptance criteria?

• Changelog entry added, if necessary
• Documentation created/updated
• API support added
• Tests added for this feature/bug
• Review
  • Has been reviewed by UX
  • Has been reviewed by Frontend
  • Has been reviewed by Backend
  • Has been reviewed by Database
• Conform by the merge request performance guides
• Conform by the style guides
• Squashed related commits together

What are the relevant issue numbers?

Closes #28934 (closed)