fix(object-store): honor concurrency limits for MinIO

[Li0k]

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What's changed and what's your intention?

Route the OpenDAL MinIO backend through the shared operator-construction path already used by S3. This makes req_concurrency_limit and http_concurrent_limit apply to MinIO as configured.

The shared path finishes the caller's already-layered operator directly when both limits are disabled, so every backend retains exactly one logging layer.

Add a regression test covering the default, request-limit, and HTTP-limit operator composition.

Checklist

• I have written necessary rustdoc comments.
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• My PR contains breaking changes.
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Release note