Add mutation to toggle whether a namespace has CS for registry enabled

What does this MR do and why?

Add mutation to toggle whether a namespace(project or group) has Container scanning for registry enabled.

This is one of a series of MRs:

• add attribute to the database and model - !147409 (merged)
• add mutation to toggle the attribute - 👈 this MR

This project adds a single graphql mutation:

mutation SetContainerScanningForRegistry($input: SetContainerScanningForRegistryInput!) {
  setContainerScanningForRegistry(input: $input) {
    containerScanningForRegistryEnabled
    errors
  }
}

The view state is managed by the security config presenter added in this MR: !147409 (merged)

Screenshots or screen recordings

n/a

How to set up and validate locally

n/a

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.

Related to #443620 (closed)