Make ConcurrencyContext exit cleanup best-effort

[devin-ai-integration]

closes #22615

ConcurrencyContext.__exit__ released its fallback cleanup_lease_ids in a bare loop, so a single transient failure stranded every remaining lease (holding slots until TTL expiry) and skipped super().__exit__(). This PR guards each release individually, logs a warning on failure, and always runs the context teardown. The same fix is applied to the v1 context's cleanup_slots loop, which had the identical pattern.

for lease_id in self.cleanup_lease_ids:
    try:
        client.release_concurrency_slots_with_lease(lease_id=lease_id)
    except Exception:
        logger.warning("Failed to release concurrency lease %s during cleanup", lease_id, exc_info=True)

The outer get_client(...) block is also guarded so client construction/teardown errors don't bypass super().__exit__().

Tests

tests/concurrency/test_context.py and tests/concurrency/v1/test_context.py each get a test where the first cleanup release raises: the remaining IDs are still attempted and the context var is reset.

Checklist

• This pull request references any related issue by including "closes <link to issue>"
• If this pull request adds or changes functionality, it includes tests or explains why tests are not needed.
• If this pull request changes user-facing behavior, it updates documentation or explains why documentation is not needed. (internal cleanup-path behavior only)

Link to Devin session: https://app.devin.ai/sessions/b7ce20e35d99461fba5c18d77790ca3f
Requested by: @desertaxle

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[codspeed-hq]

Merging this PR will not alter performance

✅ 8 untouched benchmarks
⏩ 1 skipped benchmark¹

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_{Comparing devin1/oss-8099-lease-release-best-effort (ef504b2) with main (a917cb7)}

Footnotes

1. 1 benchmark was skipped, so the baseline result was used instead. If it was deleted from the codebase, click here and archive it to remove it from the performance reports. ↩