Audit logging - new schema (#20447)

* Audit logging - new schema added, old schema removed.

* fix linter error by running goimports

* Address review comments

* Address review comments

* Example usage of new audit logging API for the updateUserAuth call

* fixed unit test on auditing updating user record

* Changed the `TestUpdateConfigDiffInAuditRecord` testcase---it failed, because this PR changes how the `meta` field is serialized into the audit log records.

* fix linter error

audit/const.go

@@ -8,6 +8,7 @@ const (
 
 	KeyAPIPath   = "api_path"
 	KeyEvent     = "event"
+	KeyEventData = "event_data"
 	KeyStatus    = "status"
 	KeyUserID    = "user_id"
 	KeySessionID = "session_id"