feat: Add some benches and integrate with Cosdpeed

[larseggert]

No description provided.

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 88.72%. Comparing base (b0e6260) to head (113191e).

Additional details and impacted files

@@           Coverage Diff           @@
##             main      #62   +/-   ##
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  Coverage   88.72%   88.72%           
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  Files           2        2           
  Lines         754      754           
  Branches      754      754           
=======================================
  Hits          669      669           
  Misses         77       77           
  Partials        8        8           

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[codspeed-hq]

Congrats! CodSpeed is installed 🎉

🆕 8 new benchmarks were detected.

You will start to see performance impacts in the reports once the benchmarks are run from your default branch.

Detected benchmarks

• many_endpoints (Memory): 3.9 KB
• simple_ipv6_only (Memory): 1 KB
• dual_stack_racing (Memory): 1.4 KB
• https_with_ech (Memory): 1.2 KB
• https_with_ech (Simulation): 24.1 µs
• many_endpoints (Simulation): 90.8 µs
• dual_stack_racing (Simulation): 25.1 µs
• simple_ipv6_only (Simulation): 19.1 µs

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[Copilot]

Pull request overview

Adds a benchmark suite for the happy-eyeballs state machine and wires it into CI via CodSpeed to track performance over time.

Changes:

• Added divan-style benchmarks covering several Happy Eyeballs scenarios (IPv6-only, dual-stack racing, HTTPS/ECH, many endpoints).
• Integrated CodSpeed-compatible Divan dependency and registered the happy_eyeballs bench target.
• Updated CI to run CodSpeed benchmarks and expanded coverage command to include all targets.

Reviewed changes

Copilot reviewed 3 out of 4 changed files in this pull request and generated 1 comment.

File	Description
benches/happy_eyeballs.rs	New Divan/CodSpeed-compatible benchmark scenarios for the state machine.
Cargo.toml	Adds CodSpeed Divan compat dev-dependency and declares the bench target (no harness).
Cargo.lock	Locks new transitive dependencies introduced by CodSpeed/Divan compat.
.github/workflows/rust.yml	Runs cargo bench --bench happy_eyeballs via CodSpeed; adjusts coverage run to --all-targets.

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[larseggert]

@mxinden ready from my side. Can tweak the actual benches in follow-up PRs.