describe_user_scram_credentials doesn't allow to describe all users

[kitor]

Description

I need an equivalent of running command
kafka-configs.sh --bootstrap-server ... --command-config ... --describe --entity-type=users

or in other words, to describe all SCRAM credentials configured in the cluster.

KIP-554 implemented DescribeUserScramCredentialsRequest where null/empty name can be used to describe all users.

How to reproduce

admin.describe_user_scram_credentials() requires 2nd argument to be list of unique, non-empty strings.
None and empty strings are strictly prohibited by implementation in confluent_kafka/admin/__init__.py

Checklist

Please provide the following information:

• confluent-kafka-python and librdkafka version (confluent_kafka.version() and confluent_kafka.libversion()): ('2.2.0', 33685504), ('2.2.0', 33685759)
• Apache Kafka broker version: 3.5.0
• Client configuration: Empty except broker address and admin user credentials
• Operating system: Linux
• Provide client logs (with 'debug': '..' as necessary): n/a
• Provide broker log excerpts: n/a
• Critical issue

[kitor]

Oh, duplicate of #1616 , closing