Fix rabbit_stream_queue:get_counters querying writer last

[gomoripeti]

Proposed Changes

rabbit_steam_coordinator:stream_overview/1 returns the member in
different format than members/1, resulting in is_writer/1 never
matching. This was changed in PR #6440. This prevents getting counters
from stream writer last as intended by PR #6442.

Tracing while calling rabbitmq-queues stream_status sq1

> recon_trace:calls({rabbit_stream_queue, is_writer, return_trace}, 20,[{scope,local}]).
1

23:42:05.259202 <0.21224.0> rabbit_stream_queue:is_writer(#{state=>{running,1,<0.1735.0>}, current=>undefined, role=>{writer,1}, target=>running})

23:42:05.259621 <0.21224.0> rabbit_stream_queue:is_writer/1 --> false
...

Let me know if the change from members/1 to stream_overview/1 was intentional and I can rework this change.

#6440 was only included in 3.12. (This is not a big issue but) this change makes a followup PR of mine easier to be applied to both 3.12 and 3.10/3.11.

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[kjnilsson]

LGTM!