Re-enable benchmark workflows with label gating

[auto-differentiation-dev]

Summary

• Re-enable libor swaption and QuantLib benchmark jobs (were disabled with if: false)
• Gate benchmark runs via benchmarks label on PRs + workflow_dispatch for reference generation
• Refactor collect job to upload artifacts instead of commenting directly, enabling benchmarkresults.yml to post PR comments (works for fork PRs)
• Update QuantLibAAD pin from stale commit hash to main

Closes #161

Test plan

• Run workflow_dispatch on main to generate fresh S3 reference executables
• Open a test PR with benchmarks label and verify benchmarks run
• Verify benchmarkresults.yml posts performance comparison comment

[codacy-production]

Up to standards ✅

🟢 Issues 0 issues

Results:
0 new issues

View in Codacy

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[coveralls]

Pull Request Test Coverage Report for Build 23858635150

Details

• 0 of 0 changed or added relevant lines in 0 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 0.0%

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Totals
Change from base Build 23855818590:	0.0%
Covered Lines:	0
Relevant Lines:	0

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💛 - Coveralls

[github-actions]

Test Results

    111 files  ±0      111 suites  ±0   5h 26m 35s ⏱️ - 13m 55s
  2 989 tests ±0    2 985 ✅ ±0    4 💤 ±0  0 ❌ ±0 
217 529 runs  ±0  217 085 ✅ ±0  444 💤 ±0  0 ❌ ±0 

Results for commit e202947. ± Comparison against base commit 3d8f365.

♻️ This comment has been updated with latest results.