Create basic non-EE NamespaceSettings::UpdateService

What does this MR do?

!36848 (merged) added a EE::NamespaceSettings::UpdateService but didn't add the usual non-EE version to match it. I'm exploring adding a column to namespace_settings in support of https://gitlab.com/gitlab-org/gitlab/-/issues/221014 and would want this (since the feature will be non-EE) but regardless, this is probably a missing piece we could be adding.

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