Sanitize LDAP output in Rake tasks

What does this MR do?

Resolves #56131 (closed).

The various LDAP check Rake tasks have long supported a SANITIZE environment variable. When present, identifiable information is obscured such as user names and project/group names. Until now, the LDAP check did not honor this. Now it will only say how many users were found. This should at least give the indication that the LDAP configuration found something, but will not leak what it is.

Checking LDAP ...

LDAP: ... Server: ldapmain
LDAP authentication... Anonymous. No `bind_dn` or `password` configured
LDAP users with access to your GitLab server (only showing the first 100 results)
	User output sanitized. Found 100 users of 100 limit.

Checking LDAP ... Finished

Does this MR meet the acceptance criteria?

Conformity

• Changelog entry

• Documentation created/updated or follow-up review issue created

• Code review guidelines

• Merge request performance guidelines

• Style guides

• Database guides

• Separation of EE specific content

• 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