Instrument usage of LDAP credentials with git with prevent_ldap_sign_in

Prior to disabling usage of LDAP credentials with git completely, when prevent_ldap_sign_in setting is enabled (even though from a logical standpoint that makes sense), we may have users who have gotten accustomed to being able to use these credentials for git operations, while the admins had the setting enabled primarily preventing UI access. For this reason we would want to add instrumentation that tracks the number of instances where this occurs

In #22325 (comment 2519098041), we have a tentative fix, but the above data will tell us whether that is a substantial number such that it can be considered a correct, but breaking change or whether it can be made.