Add Clone to Runbook.

[hildebrandmw]

When working on #1206, I ran into a situation where I parsed and stored the runbook during input validation rather than deferring until the benchmark is actually run.

Making it cloneable allows reuse of such a pre-parsed runbook.

[Copilot]

Pull request overview

This PR makes the BigANN streaming RunBook executor cloneable so callers can parse/validate a runbook once (e.g., during input validation) and reuse it later without reparsing.

Changes:

• Added #[derive(Clone)] to RunBook.
• Added a unit-test-time assertion to ensure RunBook: Clone remains true.

---

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 89.64%. Comparing base (876d9f3) to head (91e92db).

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #1226   +/-   ##
=======================================
  Coverage   89.64%   89.64%           
=======================================
  Files         503      503           
  Lines       95697    95699    +2     
=======================================
+ Hits        85786    85788    +2     
  Misses       9911     9911           

Flag	Coverage Δ
miri	89.64% <100.00%> (+<0.01%)	⬆️
unittests	89.30% <100.00%> (+<0.01%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Files with missing lines	Coverage Δ
...ark-core/src/streaming/executors/bigann/runbook.rs	94.11% <100.00%> (+0.03%)	⬆️

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.