⚡️ Optimize QDMI driver session opening

[burgholzer]

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Description

A slow provider initializer currently blocks fresh sessions for unrelated cached providers. Serialize initialization per loaded module and keep the global cache mutex limited to lookup/insertion, while preserving module aliases, failure retry, and process-lifetime provider ownership.

Remove two redundant inline-configuration copies by moving the owned session snapshot into merging and borrowing strings during synchronous parameter forwarding. A 16 MiB synthetic payload now needs one payload allocation in the snapshot/merge/construction path instead of three; parent and child sessions share the forwarded buffer.

Add regressions for concurrent alias retry during failed initialization, unrelated opening during that wait, and configuration buffer reuse. Both new regressions fail against the original driver. This change is independent of the pending Client/default-driver work in #2229 and #2230 and does not change the QDMI API.

Local validation: 478 QDMI C++ tests passed, with one existing skip (including all 106 native driver tests); repository lint and changed-file C++ lint passed. In the gated initializer probe, the unrelated open completed before release instead of waiting for the full 200 ms observation interval. These are driver-only measurements, not quantum execution or remote throughput claims.

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Checklist

• The pull request only contains commits that are focused and relevant to this change.
• I have added appropriate tests that cover the new/changed functionality.
• I have updated the documentation to reflect these changes.
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• I have reviewed my own code changes.

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[codecov]

Codecov Report

❌ Patch coverage is 90.00000% with 1 line in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
src/qdmi/driver/Driver.cpp	88.8%	1 Missing ⚠️

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