ldap: Normalize DNs when importing (#19528)

This is a change to IAM export/import functionality. For LDAP enabled
setups, it performs additional validations:

- for policy mappings on LDAP users and groups, it ensures that the
corresponding user or group DN exists and if so uses a normalized form
of these DNs for storage

- for access keys (service accounts), it updates (i.e. validates
existence and normalizes) the internally stored parent user DN and group
DNs.

This allows for a migration path for setups in which LDAP mappings have
been stored in previous versions of the server, where the name of the
mapping file stored on drives is not in a normalized form.

An administrator needs to execute:

`mc admin iam export ALIAS`

followed by

`mc admin iam import ALIAS /path/to/export/file`

The validations are more strict and returns errors when multiple
mappings are found for the same user/group DN. This is to ensure the
mappings stored by the server are unambiguous and to reduce the
potential for confusion.

Bonus **bug fix**: IAM export of access keys (service accounts) did not
export key name, description and expiration. This is fixed in this
change too.

.typos.toml

@@ -15,6 +15,7 @@ extend-ignore-re = [
     "eyJ0eXAiOiJKV1QiLCJhbGciOiJSUzI1NiJ9.*",
     "MIIDBTCCAe2gAwIBAgIQWHw7h.*",
     'http\.Header\{"X-Amz-Server-Side-Encryptio":',
+    "ZoEoZdLlzVbOlT9rbhD7ZN7TLyiYXSAlB79uGEge",
 ]
 
 [default.extend-words]