Fill in `error_message` when there's not enough brokers available

Who is this for and what problem do they have today?

Like reported in #9044, when a node, out of 3 nodes, is in decommissioning Redpanda cannot allocate a replica, hence returning INVALID_REPLICATION_FACTOR, but it's not intuitive to end users.

Upon investigating, it looks like Redpanda doesn't fill in the error_message in this scenario but just returns the error code 38. Can we fill in the error_message field which makes clients like rpk being able to handle the error in a better fashion?

TRACE 2023-02-28 14:05:56,487 [shard 1] kafka - request_context.h:168 - [127.0.0.1:59492] sending 19:create_topics for {rpk}, response {throttle_time_ms=0 topics={{name={test4} topic_id=AAAAAAAAAAAAAAAAAAAAAA== error_code={ error_code: invalid_replication_factor [38] } error_message={nullopt} num_partitions=-1 replication_factor=-1 configs={nullopt}}}}

What are the success criteria?

Redpanda to return a user friendly error message

Why is solving this problem impactful?

Better UX

Additional notes

Relevant GH issue: #9044

JIRA Link: CORE-1188

Start by reading the related issue #9044 and tracing the create_topics response path for INVALID_REPLICATION_FACTOR. Confirm how the error_message field is populated in this scenario, then verify that insufficient broker availability returns a user-friendly message and that the response is handled correctly by the relevant tests.