Add disable option for the auto-close referenced issues feature

What does this MR do?

This MR adds a new configuration option (project repository settings and project API) to disable the auto-close referenced issues feature on a per-project level. This feature covers two use-cases:

• Projects with more complex issue workflows (e.g. with review stage), where merged MRs with Closes #X shall not be closed automatically but rather after further manual review work.
• Import (e.g. Git subtree merge) of commits with existing Closes #X commit messages, which shouldn't actually close any issues.

Closes #19754 (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

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